I just purchased a used K1200LTC with about 65,000 miles on it. The seller reports that he had a problem with fuel backfiring in the cat conv while the engine is cold. I am finding that it "backfires" or rattles, or SOMETHING not only when it is cold, but all the time...not only when I let off the gas, but while accelerating, particularly between 3000 and 4000 RPM. Anybody have a similar experience...and hopefully, solution???????