I have a 99 Eclipse GS, Its been turbo charged by Star stage II turbo Kit. I never had any problems my car running lean, before when I steped on the gaz my air/fuel ratio gauge read rich, but now its lean and towards the middle, berley any rich. The way I noticed this, my check engine light came on, and the error code was car running lean. I have changed the fuel filter, I always use cheveron 91 octane and same problem. Can some one tell me what I can to fix this problem? Thanks in Advance. Tony K.

did they modify the fuel maps when they put the turbo on?
im guessing your a:f meter is the red/lean green/rich type, you should get a wideband numeric readout type to give you a better idea just how rich/lean your car is running
when you say its running lean do you mean its running leaner than b4 or its showing lean on the gauge, if the error code says its lean then its probly lean tho
have you recently increased boost and how much boost are you running now? if they havent tuned or replaced the stock computer then that would be the likely problem for best results post this in the troubleshooting forum

beleive it or not, running lean is a good thing. the problem occurs when it gets toooo lean and begins to detonate. becouse i don't konw what kind of air/fuel gage you have i can't tell you how to read it. your car is going to turn lean with a new turbo, its suposed to. and if you didn't get an ecu upgrade the engine lite will come on. i would take i back to the shop and have them check things out to be on the safe side. detonation is a very fast way to ruin an engin.