My 89 Chevy S-10 Blazer was running rough. My neighbor told me it could be my egr valve. I had it changed and now my truck is really stalling. And there is virtually no pick when I pull off after red light. My question, "Is it possible to install the egr valve upside down, which would cause the truck to stall worse?" "And if not, what else could cause the truck stall like it's doing?"

 

EGR valves are really pretty simple things. When they get a command to open they do and also to close they do. All it does is open to let some of the exhaust gasses mix woth the incoming air to get a more efficient burning of the fuel.
Did they clean the ports or make sure they were clean? I'm talking about the ones in the intake manifold.
You probably have a vacuum operated EGR (you didn't say what engine you have but I think they didn't have the electric operated EGRs in 89) and could have a vacuum line either hooked up wrong or left off.
You also have an EGR solenoid that could be bad or the connector left off. Several possibilities here. I'd take it back to where you got it changed and tell them it ain't working right. I would think they test drove it after working on it. At least I would hope so. If not, take them for a ride and show them.
PS Next time I would have the problem troubleshot instead of just listening to someone tell you "it COULD be....." and jumping on that item. You can get a lot of the "it could be" right here a lot. If you don't believe it, just reread my post. LOL

 

hey there, i just had a very similar problem with my egr, i replaced it and the problem continued. its most likely the egr solenoid. its the little black plastic peice with a filter in the front atached to the egr. its the same for all up to 94 i was told, i took one from a 93 sonoma pickup and that fixed it. also brought my NOx emmisions from 4000 ppm to 100ppm