I shoot for 11.5 with meth. I have tuned as lean as 12.0 with no issues. Timing may have to be adjusted accordingly. You should be fine running stock timing maps around 20psi. I dont believe anyone has built a boost by gear system yet, but MS does offer boost control based on rpm and TPS so you can regulate the boost in certain gears but not going WOT

98 Eclipse GS Turbo
Built motor - MS2 - Holset hy35 - Zoom Stg 4 Clutch - 57.5mm TB - ARP Headstuds - Turbonetics wastegate - 3" Turbo back - FMIC - Greddy RZ BOV - Walbro 255 - 650cc Injectors - Fidanza Flywheel - Cobra calipers w/ 13" Rotors - Oil Cooler - DevilsOwn meth injection

1981 Chevy Scottsdale
1987 Nissan 300zx - Chump Car
2001 BMW 325i