I remember doing this a while back and i put in b161 pistons (i heard they're the same as the itr). There are some websites out there that will give you the compression ratios with the head/bottom end and piston combos.

I know after i did my new pistons + Stock tune the car did run a bit rich it felt like (butt dyno) but i eventually fought adjustable fpr and fuel gauge and a vafc and had a local put a wide band on it and tunned it for daily driving.