Originally Posted by Stu @ M Developments

Afternoon Chip,
Generally speaking, at std fuel line pressure a std T3 turbo on a YB will maintain a decent AFR at up to 24psi held to the limiter. A T3 map tails the fuel off from 5k as the efficience envelope has been passed and the power drops off, so this is your danger area with too much boost. A T34 or larger will obviously drop this boost figure slightly whilst making mnore power. A real T34 map also wont start to lean at 5K as the peak power is now higher.

On my own T3 std YB chips i recomend the boost be set to peak at around 25 and hold around 22.This gives a good fuel margin and helps to control ACT's on the std intercoolers. Merry Xmas.