Sounds like a valvetrain problem,perhaps a valve sticking in the guide or a collapsed lifter?
Have you recently had the heads done?
Where does the poping sound come from?Intake,exhaust?
I went to look at his truck earlier tonight, and of course it wouldnt miss, stumble or sound like popcorn popping. Glad you made it to the truck stop! Hopefully someone can figure this out for you or at least point you in the right direction!
If it sounds like popcorn is that like a backfire. That would have to be a valve not seating so the combustion is getting blown back into the intake. Will also mess the turbo up while boosting.
If its just missing and the injectors are making a crazy noise could be you have air in the fuel lines. Many possible reasons. Lift Pump (LP) needs to be tested, inspect all fuel line from tank to Injection Pump (IP) and even the fuel filter not being installed correctly will cause it. The fuel filter is keyed so it only seats one way and if not paying attention the keys dont line up and the nut still fits on top of it.
firing out the exhaust would mean an exhaust valve is not seating and combustion is going right out the exhaust port, and I'd check it out much sooner than later. You could take off valve cover and see if anything is not in order there. are you not getting an SES light that you could check the codes it is throwing? With a scanner you could also turn off injection to individual cylinders.
Do you have a history of good performance with this truck?
I'm assuming it's a 97 from your name, and I get that it's a 6.5 from your first post. How many miles on it? What mods have you done? Maintanance state? Is it running on #2 or B20?
Please take a minute to fill out your signature as completely as possible, so we know what you're driving. It would also be helpful if you could fill out the diagnostic checklist and paste it into this thread, so we could 'hear' and 'see' your truck.
As far as i know the truck is a 97 2500 reg cab long box. It has an F vin engine and the truck has lots of miles but the engine has been changed recently.(probably within 50,000 miles) The truck was a fleet truck from a construction company with very good maintanance. The only mods that are known is upgraded exhaust. It also has a new PMD. The only code that was stored when i checked it, was turbo boost sensor. I erased it, informed him that the grounds need to be cleaned, and tried making it miss, but it never did. Oh yah........I also told him about this site!!