1989 TBI 350 EGR Problems?

Here is my situation....I have a 1970 Blazer with a 1989 350 TBI Suburban engine. The engine recently started to bog down and die at stop lights after coming from full throttle. I am able to observe the EGR valve open as I push the throttle linkage, but it stays open once I release the throttle. This causes the engine to idle very rough and completely kill it self at times. I have taken the EGR and cleaned it, no GO. I have replaced the EGR module, but still the same problem. The vehicle runs fine if I plug both the EGR and EGR module with vacuum caps, but I would like to isolate the problem. Any ideas?