I guess this is where a boost guage would be good. My old 95 was down on power and smoked quite a lot. Finally found a bad wastegate solenoid and improvement was dramatic. I currently have a PO299 code and low tubo boost. I would hate to tow anything until its fixed (Mon. I hope). My light throttle driveability and mileage is still good though. Sure sounds like low boost could be an issue. How has the dealer been in responding? Maybe a different dealer is in order. Good luck!
2005 Regular cab, LLY Allison, new 7/05