Have 08 6.7L. Have done full turbo-back exhaust replacement, done EGR and EGR cooler deletes. Now I get a belt-like squeal when I accelerate, and low power under load when towing. Low power was an issue before EGR/cooler deletes. Have Race-ME race only tuner, tried economy and tow selections, no help there. After a few hundred miles of towing, squeal is subsiding, but this pig wont climb hills to save it's life.
The nice little light in the overhead console comes on and tells me service required, see dealer now, but when stopped, no DTC codes have been stored. Starts with no codes, but service warning comes on after about 10 minutes of driving under towing load. No ill effects for normal driving without load.
Pulling out my already too thin hair, any ideas here?

 

Can you add more details to tell us what other mods you have done? That may help you get some suggestions.
Auto, or manual trans?
Which programmer?
IS the squeal consistent with rpms?

 

Auto trans, tuner is "Race ME" and squeal changes pitch and sound with rpm, much like the drive belt would do, but that has also been replaced.
Straight exhaust with only muffler, turbo back, and egr and egr cooler delete are only mods.
Oh, and as mentioned, the squeal seems to be going away as the miles go on after the egr/cooler delete.

 

Sounds like a leak in the exhaust side subsequent to the EGR VALVE/COOLER deletes. Check all the gaskets and block off plates. Also, could be boost leak. Check hoses to intercooler.

 

Ok, so, figured out the high pitched squeal, yes, it turned out to be an exhaust leak at the block-off plate at the rear, the kit said to use the old gaskets. Did so, and it didnt seal well, acting like a saxaphone reed! Now, the gasket is blown out and leaking, so need to replace those. Still have the low pulling power tho, wondering if that might be caused by a stuck slider in the turbo? I read in another thread that there is a slider in the turbo that is notorious for sticking, can that cause the low power for hills, etc?

 

Check your clamps on your inter cooler hoses. If there's any psi getting around those, she'll bog down on ya quick. I had a cooler hose blow off on a dump truck one time and I lost power and blew smoke like crazy.

 

By slider on the turbo, you mean the variable vanes, right? Do you have a boost gauge? What kind of boost are you seeing?
If the exhaust brake is working on command, the turbo vanes are not stuck.

 

Ok, the EB works just fine, and when I was running a "legal" Bully dog, the boost raised and lowered as it should, so I guess it isnt the vanes. I did find that the gasket on my rear EGR cooler delete cover plate had blown. Seems H&S didnt correctly figure the plate thickness, and the threads on the stud ended before the plate was properly torqued down. Replaced the gasket and installed some washers to compensate for the plate. Havent yet gotten the truck out with a load to test it.