I have a 99 f 550 7.3 with 200,000. Just recently the fuel system was contaminated with engine oil. I replaced all 8 injector seals and cup sleeves. Replaced the rail fuel pump and fuel filter. The contamination is fixed, but after a couple of the days of using the truck it made a hissing noise from the turbo and just started running rough with heavy white smoke. It wont go away when engine is hot. It ran rough the first time i started after i completed the job, but it went away. now its back for good!!! I have a modis scanner to use, but not sure what to look for. I know of the buzz test, but if that is ok what else do i need to look at! Any info will be appreciated.....