becareful with the pistons.
Im not saying this will happen with the NA pistons (which if i was going through the trouble of swapping pistons i would never use, high cr + boost...piston killer), You have to watchout for the piston to valve clearance. Depending on the compression ratio increase you may need to have the pistons notched for valve clearance.
You have to take into account the cam specs as well because this will affect how far the valves protrude into the combustion chamber (obviously)
Your best bet would be to get a set of custom pistons made specifically for the GTi-R SR20DET.
The FWD NA SR20DE pistons come in either 9.5:1 or if you can find the JDM or UK spec 10:1 pistons. These will not yeild their respective compression ratios in the GTi-R SR20DET vbecause our combustion chamber is larger.
I do not remember both combustion chamber sizes at the moment but i will research it. I am confident that the FWD 9.5:1 cr pistons will yeild at least 0.2cr points lower when used in the GTi-R SR20DET.
You will not beable to run 1 bar on optimax (and no water/methanol injection) on a compression ratio any higher than 8.8:1 (you MIGHT be able to run 1 bar on 9.0:1 but for saftey i would limit 1bar every day usage to an 8.8:1 motor)
If you are talking fairly high compression ratios (10:1 and up) then you will be severly limited with your boost on optimax. With a 10:1 cr i wouldnt DREAM of running more than 10psi on optimax.
11.5:1 is the limit on pump gas (still being able to get to redline, sure you might get away with 12:1 but i garuntee you wont be able to rag it)
11.5:1 and i wouldnt dare run past 6psi on optimax.
This all changes on race fuel though. Rally cars can run stupidly high compression and boost because they run race fuel and water/methanol injection?? (not sure about the water/methanol injection but it seems likely).
Another thing to take into consideration is the head bolts. You WILL NEED UPRATED ONES!!! The stock bolts WILL NOT handle high compression and boost....no exceptions