OK this is not my car, and I'm not convinced that it is a tuning issue yet.
The car is an 04 STI with modified stock injectors (scaled to 750 in Enginuity) with a Perrin BigMAF and a Turbosmart BOV (atmospheric). Rest of the stuff is typical.
Please don't lecture me on the BOV. I know its bad with MAF.
The car dies when coming to a stop with the clutch in. It stalls more readily if the brake is more forcefully depressed (less vacuum).
Logs of the period just before the stall show that the ECU is either pulling fuel or adding fuel depending on how I scale the MAF at low load.
Here is a typical scenario. The car is decellerating in gear, clutch in, brake lightly, RPM drops very low to 500 (idle is set to 950), car gently stops, idle drops to 200 RPM, car sounds like rich, but AFR can indicate lean, car idles in the 400-600 range for ~10 seconds, car recovers to normal idle at 950 and AFR of 14.7.
I cannot stress enough the long period of low speed idle before going to the set point. 10 seconds is a long time.
I've tried rescaling the MAF. I've tried unsuccessfully to eliminate closed loop fueling from the idle area. I can post a log but I think the description is more informative.
Driving me crazy, making me feel stupid. Please help.