I have a 2004 f-250 6.0 - runs like a champ, but when you get firm on the gas and back off I hear 3 spit backs kind of like an exhause leak and can be felt in the floorboard. Any thoughts.

Check your turbo. Be sure to only use full-synthetic HDDO with your turbo.

Check your turbo. Be sure to only use full-synthetic HDDO with your turbo.

I too am a die hard do it yourself but only on gas engines, I know nothing about diesel. With that said I have a couple of dumb questions here. HDDO?
Also it seems like the turbo is working I still have plenty of power.

HDDO--Heavy Duty Diesel Oil. Examples are provided in the link below:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-8.html#post1415281

Coking can interfere with exhaust flow.

HDDO--Heavy Duty Diesel Oil. Examples are provided in the link below:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-8.html#post1415281

Coking can interfere with exhaust flow.

I had a friend tell me to clean or replace the EGR valve but from what I have read that would show a different sign of problems. Sounds to me like your telling them in a nice way that the turbo might be failing. I bought it used 89k miles and just noticed that it has a reman turbo on it now, so it's been replaced before. Will the turbo go completely out before the truck stops running,

Without using full-synthetic HDDO, turbos are a constant source of problems. Since they are powered by the exhaust, performance problems show up pretty fast. It's possible what you are experiencing, now, are signs of turbo trouble. The truck will keep running, but the performance will fall off so much that you won't be able to stand it.