This is one of the first things I learned in diagnosis. A rag being sucked inward at the tip of the exhaust in rthyme of the idle is a burnt exhaust valve. This is the first thing I noticed helping a friend out with changing the spark plugs. My buddy thinks he knows about fixing cars, he can do the work but hes a retard. I get a call, "Kenny get over here now!" I get there and hes telling me he broke 3 spark plug wires when changing the plugs on his 00' Ram 2500 and that he "repaired" them. Hes also telling me he messed up the firing order, he said that he tried a bunch of times running it trying to get it right. So i'm thinking OMG when he starts it up, seems to idle, puts it in drive and it bogs and almost stalled. No fear, the expert is here: I told him to get new wires, we goto the store and get em. I prayed that #1 was right on the order since Dodges are the same as Chevy 1 8 4 3 6 5 7 2. I took off all the wires except #1 and started from there putting the new wires on. I start it up and it ran a little better, slightly shakey though. It seemed to sound wierd at the exhaust tip so I got a rag and it would be sucked in about 1/4 inch in rythme with the exhaust, suck blow suck blow /forums/images/graemlins/shocked.gif. I told him its a burnt exhaust valve. He doesnt want to believe me because he said it ran good until he did the tune up. We drove it around, I told him to floor it and it didn't go anywhere, then the MIL came on. I figured it was the O2 code acting up because one cylinder isn't firing. When I think of burnt valve, I think of a sick race car engine, not an engine after a tune up.