My 990 with 20k miles, the engine RPMs when you are not accelerating goes up and donw all time, somtimes stay up for some seceonds and then goes down. I cleaned all injector, injector body, fuel filters, etc... but it still do the same, somes idea what can be the problem ? KMT service told me that I have to change all injector body, but this cost a fortune and I dont think this is the problem. Thanks for the help !!!!