I would predict that a 1mm larger inlet valve would drop boost pressure slightly not increase it.

kojab
I would predict that a 1mm larger inlet valve would drop boost pressure slightly not increase it.

I think that's what he meant anyway

I was talking in reference to any potential power gain.

Well one thing sticks out a mile and that is Jason and Rob have proved you don’t need 1mm bigger valves to make impressive power.

kojab
Well one thing sticks out a mile and that is Jason and Rob have proved you don’t need 1mm bigger valves to make impressive power.

Pretty much convinces me.

That is a point but how about reducing the standard valve size by 1mm? Would you make the same power??
Don't think so.
The larger will produce more power. Bigger capacity engine will too, bigger turbo will too, bigger budget, etc etc.
If Ferrera cannot help you simply fit what a large percentage of the racing community use. Supertech.  Proven over the whole planet so I am sure it will work with your engine. In fact I have a set of Inconel 1mm oversize valves that I would be happy to pass on to you at a heavily discounted price.
 

I don't want to risk using Ferrea again. I will be trying to get my money back.
BTW Steve - "The Inconel valves are only used on the exhaust side, it is the only side that it is needed to use a higher temperature alloy"
Thanks for the offer though

Any engine performance is based on flow rate. If you can improve the flow, you can improve the performance.
With a turbo engine, you can indeed improve performance by increasing boost, which ultimately improves flow, though you get the side effect of additional heat. Wouldn't it be best to improve the natural flow of the engine thereby requiring less boost to get the same power and decreasing heat?
Oversized valves definitely improve performance on a NA engine so why not a turbo engine too?
I bet you have all upgraded the exhaust systems on your cars. Why? To increase flow. Why not improve it on the intake side as well.
Sure some of the guys have impressive power figures with their street cars. I'd like to see those engines perform reliably under race conditions. It is a totally different story - much harsher with a LOT more heat being generated. Decreasing heat is the most important thing to chase in a turbo race car, not power.

I'm thinking of buying Supertech TIVN-1012 stainless steel with black nitride coating as per this page -
http://www.supertechperformance.com/cat-ivalves?mk=10&ca=398&en=60
Does anyone object?

1mm of extra valve versus a different valve lift versus more duration etc etc etc 
 
Apples and oranges guys! there are more than one way to skin a cat. 1mm is stuff all, and is only the valve not the whole port.
 
Upping valve sizes is quite old school for heads with rubbish flow and not as important for a 3SGTE/5SGTE than a N/A engine. Our heads flow quite well and really a clean up of dags, port matching, different valve seat angle and "maybe" some bowl/throat work is all that is required to be considered full on in my eyes.
 
Also boost is a function of restriction not necessarily just "flow"
 
These are all the reasons why i did not do this to my own engine and only cleaned up dags, 3 angle valve seat cut and port matched the ports. Glad i did not just buy them because "everyone on MR2OC uses them" which was the way to go at the time.