really lean; problems

[Antman2185]

My car goes really lean at light throttle. Immediately after going from say < 5% throttle to around 17-20% throttle, my AFR goes lean. My o2 gauge stays red for a bit then gets normal. Logging my AFR w/ dsmlink it says 18:1. I can not seem to change it. When it hits really lean the car does not seem to accelerate, it lags. I don't know what wrong.

I was looking and I believe I have an air leak between the turbo and exhaust manifold. I could feel air coming out and my heat shield was all black in just that corner. Could this be the cause of my problem?

Thanks,
Anthony

 

[Quasimondo]

It's lagging probably because you're knocking so much that the ECU is severely retarding your timing.

Did you check for boost/intake leaks? What about the condition of your fuel system, pump, filter, regulator, etc?