My friends chevy truck 1995 1500 2wd 305 has a problem with stumbling and hesitation at low rpms and idle but once he gets it to high rpms the problem goes away and it seems to run fine untill he drops it back down. Hes changing the plugs tomorrow but I suspect that it could be the egr? Could the egr stuck open cause stumbling at low rpms and running fine at high rpms? I checked it for codes and found nothing but a 12 and that means everythings fine but its not. If the plugs dont fix it im thinking of pulling the egr and blocking it off to see if thats the problem.

How many miles on the motor?

About 112,000 he said the egr valve has been replaced before

unplug the egr vac line as a way of testing. if it "works" fix the egr problem.

We did that but nothing happen so that makes me think thats its messed up on the inside

Check for vacuum leak, too...

X2 check for vacuum leaks, fuel pressure, compression, etc.

The EGR is not likely the problem.

Well turns out it was the EGR ,pulled it off and it was carboned to hell so replaced it and now truck is back to normal, thanks for all the help.