I have an '88 silverado 5.7 litre with about 250K miles. On hot days it will stall when I slow down to make a turn or stop. After a couple minutes it will start right up but still does the same thing. I was told it was the EGR valve but it only helped for a short time. I replaced it again thinking maybe defective part but it is still doing it. I have also replaced the fuel pump and relay about 6 months ago. Please help.