I have a 1988 iroc w/305 TPI.It runs rough then dies only at stop(never under acceleration.I put it in park and restart,then it runs fine. This happens every other day , sometimes every other week.Also engine pings,My mechanic tuned it up and checked the timing.Still pings ,still dies.DO I need another ECM. I have had two different mechanics look at this.This has been an intermittent prob for a couple years.Do I need a new ECM?