911 short run engine stalls
 

I just bought my first 911 (1990 C4 conv.), after I sold my 968. The engine wasrebuild at Motor Meister in California with the bigger bore package to 3.9 liter engine.The engine nowhas 10.000 mls. after rebuild.The engine stalls sometimes after a short run, when I come to a stop sign. It starts right up with no problems. I have no problems on longer trips, but in the city, stop and go. I have good gas mileage and the car does not smoke, and idles good. I do all the maintenance myself, and all the components were replaced, after rebuilding the engine. Fuel pump is ok, and fuel filterwas replaced. I tried to get the problem solved with a Porsche dealer, but no luck. Any suggestions. Thanks.