The problem that I have is that it runs poorly but only intermittently, sometimes it runs fine. It's not misfiring. I rebuilt the Fuel Reg. and replaced the lp filter since the truck has 11,000 + hrs. Tuned up as well. Getting spark at each plug. No check engine light, but this first code I see from it's history is 190-4. I don't have the service password to erase them and I'm not getting a code at all. I believe the throttle body is getting stuck, I hear it click every time it's running poorly....