Exhaust brake engaging on its own when not turned on and during normal exceleration

[Angelia]

Need help. I have 2008 3500 6.7 we did the delete on it a couple yrs ago. Having trouble with what seams to be the exhaust brake engaging while driving. Even when it is not turned on. You loose exceleration and it sounds like the exhaust brake engaging. The only way to regain truck is to put truck in neutral and let it come back to idle rpm or stop and turn off. It almost cause us to get into trouble in traffic a couple times. Don't understand what is causing this. Any ideas?

 

[xcc_rider]

Could be a bad turbo actuator or sticking turbo vanes. No way to tell for sure unless hooked up to a diagnostic tool and watch the commanded vs actual on the values when it happens.
You can replace the actuator and see if it helps but as I understand it, it's a crap shoot to find a good one.
Being it's a 2008 then you have the first generation turbo. The newer ones have upgraded coatings, metallurgy and a stronger actuator so it might be time for an upgrade.
Did you have the J-35 ECM flash prior to deleting? There should be a sticker in the engine compartment indicating the flash was performed.