My 87 is stumbling

[f.monroe]

There have been a couple threads on this similar subject lately . I didnt want to hijack anyones thread so I will ask my questions here . My 87 stumbles and I checked it only to find the EGR activates with the opening of the throttle . If you hold the throttle just off idle , it will stumble and surge like it has a large cam or something . I can see the EGR open as the throttle is opened . I unplugged the EGR and the truck runs fine but I get a little detonation under a load . How exactly and when should the EGR operate ? I unplugged the electrical connector from the Egr solenoid( I guess that is what it is ) and the EGr does not activate . Something appears to be signaling it causing it to open prematurely . Temp sensor ? Frank