So let me start by saying I haven't been on since January 24 2012!!! Been busy. I no longer work for a dealer. I now work for an independent that specialize in diesel trucks (GM, Dodge, ford). I need help myself now. I have this LML that has a sudden loss.of power under load. Fuel restriction gauge barely made 10 inches when it failed. When all is good it will climb to 15 inches restriction with no issues (may need an AIRDOG installed). There are no Dtcs at all. I smoke checked the induction system and found nothing. I did replace the MAF sensor with an AC Delco because the air filter was not sealing properly and the sensor was covered in a fine dust that would not clean off. Turbo has full sweep. Makes 200 MPA fuel.pressure when all.is good. Pulled FRP #1 On pump and found no metal debris on screen of regulator. MAF grams per second exceeds 400 under load. Jas a 4 inch exhaust that appears to be MBRP. Dude bought truck used from a used truck and it came to him deleted and that is why I have no idea who made the tune. I am an experienced DMAX Tech. I have no clue where to go with this. I have a feeling the custom tune has caused the ECM to not be as sensitive to the drivabiloty issue. Any help here will be great. ☺☺☺