So my next upgrade is the replace the injectors and fuel pump. Only thing is I have heard that the fuel pump is a really **** job on a SW20. Why is that for anyone who has done it? Also what's a good fuel pump to upgrade with?

It's not that bad if u have your eng out as access to the pipes arc at the rear of the tank isn't the best otherwise. Also make sure your tank is next to empty.

yeah its just the placement of the tank/pump that makes it a PITA but can be done if you have time, and be careful doing it.
 
As for fuel pumps, there are a few out there, depending on power levels, but most people run with the Walbro pump, although can be a little noisy. I have just put in an Aeromotive Stealth 340lph, but cant let you know how it goes until every Feb after the tuning 

for the price i'd go straight for a aero340.

ive done it several times. pita and fiddly esp when doing it yourself. i used a jack to help lift it in etc and support it whilst fittingthe strap etc.

haven't done it (yet) but i heard its a nightmare...
Supra TT (Denso) pumps are a good reliable upgrade too if you want it OEM quiet. 

Its mainly a PITA due to the lack of space around the fuel lines and under the car.  If you have access to a pit/hoist, the job is not soo bad :) It is also worth noting that the gen1 cars had a drain bung in the tank that is removable with an appropriately sized socket, so draining the tank isn't too bad.
 
Doing it on the ground with a jack requires minature hands to get up behind the engine to undo the clamps :D
 
While you're under there, its also a good chance to inspect your coolant passages and clutch/brake lines for any corrosion or signs of rust.  OEM Supra pumps are a quiet, no-nonsense upgrade, but I have heard Walboro make some good 440LPH pumps and a few kiwis use them.  They tend to be a bit noisy though.

first of i suggest having someone help you who has done it before, there is a certain order you need to do things to make it easier, for example dont forget to disconnect the plug from inside the cabin before you remove the tank (my first mistake).
 
second of all it took 3 people for us to get the tank back in the car, as you need people to hold the tank while you connect the hoses back up. you cant mount the tank and later connect the hoses as there isnt enough room.
 
so find 2 friends who are willing to help, and someone who has done it before otherwise it will be a c**t of a job!!!!

where did you disconnect the lines? i did them were they connect behind the heat sheild.

Ive always bolted the tank in, And then connected the lines without a problem

Hmm, we'll I don't have the engine out or do I know anyone who has even own an MR2 let alone done it before. Sounds like the type of job I hate the most (ones with no room to work, which is the case for a lot of them with an MR2 as I have found).

How much did the Aeromotive Stealth pump cost?