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kinda runs like ****, that is what got me thinking about a chip was talking to a guy that burns them and he asked about that. Said there is a part of the program that runs the air valve for the pump. The truck falls on its face when getting on it.
Napa lists this smog pump for a 1991 R3500 with a 454. NAP 51278. I then found some info on motorhome P30 chassis with a 454. On label it says 1990-1994 the smog pump was eliminated. In 1993, I ordered a C2500 Suburban with a 454 and I don't recall a pump on that one, even in California. The cat was just IFO the rear axle though.
Yeah, nothing should need to be done to it. At least regarding the smog pump. How did you plug the holes, and does it have any exhaust leaks right there at the manifolds that could be confusing the O2 sensor? I think it’s something else. Any check engine lights?