Knightrous

track_mr2
I really don't know how using stock style throttle bodies on a  ITB setup would work. Are they cable driven? Most factory throttle bodies are cable driven, so you would need to run a the main cable system to some kind of winch system to pull the throttles open?
One of the throttle bodies would need to have the TPS mounted on it where the others wont.
If you are leaving the injectors in the origional factory location and just getting ITB that are basically a buterfly, there are a lot of cheap custom made options for billet buterflys. They have individual throttle stops and are very compact, also have mounts for ram tubes. The EFI Hardware stuff has the injector tube moulded in as they are usually used for webber carb to EFI conversions, thats why they are pricey. Also mounting the injectors as far from the cylinders as possible gives better atomisation and gives better power.

I believe they are talking about the Factory 4AGE 20V Blacktop ITB's which solve all the issues you raise and are commonly used in ITB conversion for many other motors (4AGE 16V, 1UZFE, 3SGE)

 
The 4AGE ITB's can be sourced for $100-$200 a set, which is cheaper then a single individual ITB from EFIHardware.

I have been looking for the 48mm, but cannot find any. There are plenty of 45mm units which based on a chart I have found, will manage the output I can get from the head combo I looking at. 45mm are $200 a set.
The efi hardware is great, but its really aimed at higher budget engines. Its 5k for the 2GR. Way out of my budget.

B24
If I can get the mold sorted, I can have a manifold casted for under $500. Now who has that 3D printer..

Send me the motor for a few weeks and I'll see what I can do ;)

The 4AGE 20V ITB's separate into individual units once removed from the manifold. Each ITB has an adjustment screw on the linkage joiner to allow adjustment to sync them properly and a return on each throttle. Here is an example of how someone use joined 6 of them together for an RB20DE

 

track_mr2
They do look like a good option price wise. They look paired up though, so do you need to cut one pair to split them on each bank? For reference 6 48mm on a  3.1L were slightly bigger then necessary. The correct size for me to run would be 6 45mm throttle bodies but that was 3.1L with a single over head cam. So on a 3.5l quad cam 48mm should be about right, maybe even 50's are doable..I think you'll still find some challenges using the 4AGE setup but they will just be small things, like pedal feel through spring return rates, syncing issues etc...but I'm sure you'll be able to find solutions for them as they pop up. I have noticed some other V6 ITB kits for sale that are just above the 1k mark for things like VQ53's. Possibly one of these kits adapted to the 2GR might an option if the 4age setup doesn't pan out. 

I have contact the people selling the VQ35 throttle bodies but they do not sell anything separately so I cannot go down that path. Also not sure on the exact spec of there throttle body. From what I can gather, the tapered units are the best option. The 4AGE units are tapered but I cannot find any available at this stage. There is also the option of fitting three twin throttle bodies if I cannot find anything in the next few months.
 
Have you heard of water injection being used in NA application? It would be great to hear the plus and minus of this option.
How much fluid per hour would be a helpful figure.
Would it be best located in the plenum/air box or utilize the injector ports as the injectors will be located higher in the inlet port/ with the injector or simply add a bung to the inlet runners then fit the spray nozzle.
My car has the water injection set up from the turbo engine so if there is a gain without too much pain from using the water/methanol injection, I may give it a go.
 

I've never seen water injection on a  NA so can't really comment on any gains or issues but personally I wouldn't have thought it to be worth while for the effort especially considering the amount of work ahead of you for the build. What RPM are you planning to run from this engine, I'm guessing it will be spinning quiet high to warrant the ITB setup? I can give you some power figures that might be useful from my own experience. On my single OHC L28 stroked to 3.1L with 10.5 compression, mid level cam (74 degree's), port work etc...with 6 48mm throttle bodies in a  240z I was 165rwkw with a  7,000rpm redline. I could have run tuned length headers and a 78 degree cam to make closer to 200 rwkw with a 8,000 redline but I didn't want to lose my bottom end torque as the car was used on the street too. By comparison another guy fitted a RB25 with 6 45mm ITB (same EFI hardware gear), exhaust etc...and was only able to make 125rwkw, on a RB with twin cams and cross flowed head. So its not always a bolt on and gain with newer engines, I think they really need to be spinning some high rpm to get the full gains. He was quiet surprised as he changed from an 2.8litre single OHC L28 to this RB25 expecting to gain but lost out. His old engine L28 with those throttle bodies was making just under 150rwkw's.

The biggest problem (IMO) from my observations is that when people convert to ITB's, they do not maintain sufficient length of intake runner. What this does is requires you to use higher RPM to get the same wave order as the stock intake or you end up using a lower wave order at the same RPM, which has less power potential (anything after the 5th wave is pretty marginal).
 
Example. The 4AGE 16V Bigport has runner lengths around ~450mm long before reaching the main plenum chamber, but when fitting ITB's with an adaptor, that is easily brought back to ~300mm or less. With a 480mm runner length, 7000RPM is approx the 4th wave order. If the intake runner is shortened to 320mm during the ITB conversion, this puts it on the 6th wave order at 7000rpm and you lose the performance, hence why you need to rev it harder... On the flip side, if you can get the runner to 600mm, you can get it onto the 3rd wave order at 7000rpm but you will also pick up the 5th wave order at 4200rpm.
 
Toyota did similar things with their ACIS intake design to ensure that they could have good low down torque by having long runners through a divorced chamber with a butterfly that would open up later on in the RPM, essentially shortening the runner length.
 

This is found on the 3VZ and 1MZ motors as well.
 
The other thing to consider is, just because your going to ITB's doesn't mean you have to go to an open air velocity stack design, there is plenty of performance available with a plenum design (F1 is an example).

Be careful with OBX, there have been many stories about throttles sticking with their gear. Just a FYI (looked into these myself before purchasing what i have now)
 
Here is a video of the M3's water injection. You can tell by watching this it is not ideal (pooling, splotchy spray at times, not fine enough and in general too much water) but it gives you a idea.
 
http://www.youtube.com/watch?v=EyPrYBbUB3w

Good to know. When I saw the price I blown away by how much cheaper it was then what it cost me to do with EFI Hardware gear, which was around 5k all up by the time I had finished. If I had to go down the path again I would have bought these on price before hearing your guys stories about it.