On of our work trucks is having ongoing issues. 2004 Chevy 2500 6.0L ~50K miles mostly idling around our property It's been throwing P0300 codes for a long time, some overheating issues as well. Getting most of this third hand, it's been to our independent service and local dealer a bunch of times. New plugs and wires, new waterpump, MAF cleaned back in December June Dealer receipt shows a failed injector balance test, they did a top end cleaning, code cleared up for a while July dealer service has another top end cleaning and advice to "drive as much as possible to free up sticky valves" I think we may have done another cleaning, soaking it over a weekend type thorough job. I see a whole lot of "dump some stuff in and hope for the best" and not a lot of actual testing and diagnosis. Injector test failed, why are they not replacing injectors? Another guy's buddy suggested a quart of ATF in the oil. ideas? advice? dealer is pushing to buy a new truck, the grounds crew is eager for a big Diesel that they'll do the same thing to.