Everything has been going out lately on my 780 turbo. The heater hose burst the other day, and I wound up replacing alot of other hoses as a preventative measure. I also flushed and put in new coolant. I also too the time to clean out my airbox, change pcv valve, clean throttle, etc. Everything was running quite well for a period of time, but now I have found that on deceleration (coasting and breaking) that occasionally the tach (and engine) will jump about 500 rpm, producing a sort of jerk which... well, is at least undesirable. I have a 90 740 turbo, which generally gets better mileage and has better pickup- Im told the difference in pickup is due to the 740 having a smaller turbocharger- indeed this is probably true because even though the 740 is faster off the line, the 780 definately has more high-end passing power. Anyways, does anyone what could be causing this random "bump" in RPM's when slowing down? I suspect the 02 sensor and/or Air mass meter, but have no real reason other than deduction to believe one of these is the culprit.