eCtune

Race car only. 15PSI. what would be your target AF, and what would be the leanest you'd go.

Aftermarket pistons?

what gas are you on? and what kind of racing?

on 93 or 91? if its on 93 and its turboed i'd shoot for 11.5-11.8AFR at wot.. if its on 91, i'd run it a tad bit richer then normal, Leanest i'd accept is 12.0's..

after market pistons, valvetrain and sleeved block, 94 octane, road circuit.

are you running loose clearances (Piston to wall) on the motor? or is it gonna be tight? Basically at 500HP on a road course i'd start out rich like 11.0 but I'd probably end up alot leaner by the time I was done dialing it in. if its on good gas, has a good cooling system and theres good piston to wall clearance there should be no issues running this car in 12-12.5 range.. Running it leaner will yeild much better transient throttle responce while in boost as well as reduce fuel comsumption GREATLY.. Main concern is keeping the IATs and ECTs in check. I'd start rich, 11.0 but if the car stays at good temps while under hard load on the track I'd start leaning it out, it'll just plain run better like that. If you can get away with it on 94oct, I'd run more timing and less boost. this is one of the few times I'd do this. The reason being is that with the standard less timing more boost, your EGTs and IATs go way up, and on a road circuit where you'll be constantly in boost this could cause turbo longevity issues as well as heat related problems. You want to keep your EGTs and IATs down. I'd definatly get an EGT probe so you can keep an eye on it.