Aftermarket pistons and lowering comp. ratios

[T0nyGTSt]

I need new pistons.

I'm thinking about either forged pistons or GT-R pistons.

Now while I have the opportunity, I'd like to get pistons that lower the compression ratio from 9.0:1 standard to something like 8.5:1 - but I do not know the affects.

Of course I know that lower comp. means you can run higher boost and maybe less octane rated petrol but is there any bad points?

Less off boost power?

Lower fuel efficiency?

Also where may I get GT-R pistons, perhaps even N1 class pistons? Preferably new.

I'm not hung up on 'forged' pistons. This is a streetable car after all...

T.