Don't think I have an air injection system - wouldn't that require an air pump? Don't see one of those. I've suspected a vacuum leak but so far haven't found any. Went to a shop, they said they could find the problem with their engine analyzer (they did pass me and gave me a new windshield sticker so I'm good for another year). They said the codes indicated a bad EGR valve. I have just replaced that - it's a pretty straight-forward replacement, is it possible I screwed something up when I replaced it. I did notice when I replaced the EGR valve that the body of the new valve was a little thinner, about a half inch, than the old one. Could be I installed the wrong valve? This is very frustrating, but at least I have another year to fool around with it without fear of getting a citation for an expired sticker. The truck actually runs OK, doesn't stall and runs good at high speed, just surging on acceleration and a rough idle. I can live with that except I fear I am doing damage to the engine running it like that. Again, I really appreciate you advice.