I have 99 F350 SD w/ 7.3L Powerstroke. Starts sometimes and other times starts and runs for 5-10 sec. then blows white smoke and runs really rough and loud. Sometimes runs through the roughness and runs normal. Other times dies and will not start. Took it to a diesel mechanics shop where he changed out fuel pump, low press oil pump, fuel back pressure valve, dropped tank and cleaned out, blew out fuel lines, replaced filter several times and on and on and on. It will start and run fine at his shop but get it to my house back to the same old antics the next day. Any suggestions out there.