83 22r with 194k miles -- Last week I had a muffler shop install a new cat and magnaflow muffler. They didn't have the downpipe, so they left the old one. After the new exhaust, the engine ran great, it seemed to pull much better and sounded throaty. I still had some exhaust leaks that I could hear, usually when the engine was cold. The truck hasn't been driven much since the new exhaust, just home from the shop and 1 trip to the grocery. Today I was driving to work and noticed that the exhaust sounded funny, like a card in the spokes of a bicycle wheel. Hmm, I thought the exhaust leaks maybe. Well, then at the next stoplight at idle the engine was really vibrating, loping kindof. I go to take off and I almost kill the engine, the power is WAY down. Anyone have any thoughts? It still idles at a consistent speed, around 900rpm, just shakes quite a bit, it did backfire a couple times when I hit the gas.