Quote Originally Posted by Bug View Post
Do you have an EGR valve on it? Sometimes when that goes bad it will run like crap. It usually sets right next to the carb close to the middle of the passenger side. Never checked the compression on a motor that had a bad EGR valve though.
All the EGR valve does is modulate to introduce a measured amount of exhaust gas into the air/fuel stream to slow the burn time, equivalent to increasing the octane rating in the fuel. I don't see how an EGR could affect compression measurements, but if my understanding is off I'd like to learn.