Hi folks. So my '86, after it warms up runs fine at higher speeds but when I let up on gas it chugs. As soon as I step on the gas it goes away and runs fine at 50 and above. Slow down and it chugs.
????

 

While it might sound counterintuitive, I would check the fuel pressure first.

 

I will try that. Thanks.

 

I had an 87 IROC-Z that would start fine but would hardly go until you got up to 30 and then it was just fine. It was the fuel pump.

If you don't have a fuel pressure gauge, you may pick one up at Harbor Freight for about $25.

 

Hey thanks. I'll be checking that out.

 

Let us know what you find.

 

Check your EGR valve. It's supposed to open under acceleration and close on deceleration. It could be stuck open and feeding exhaust into the intake at inappropriate times. A vacuum gauge tee'd into the EGR vaccuum connection and taped to your windshield will reveal this.

 

Thanks Fred. Will give it a shot.

 

Even if vacuum is present, the EGR valve could still be stuck. You'll probably have to just remove it and visually check to see if it's stuck open.
How did the fuel pressure check out?