My truck is a 2007 6.7 lt Cummins diesel - first generation of the 6.7. It is equipped with a Bullydog GT and Banks air intake system. About 2 years ago I installed the air intake and at the same time I upgraded the GT software. About this time I believe it occurred, I get this intermittent noise that appears to be coming from the turbo side of the engine - it is quit intermittent, sometimes I go 1000 km and nothing, sometimes happens several times a day. It's kind of a "thwunk" or "pwop" sound, sometimes 3 or 4 instances, and like I say sometimes go for days and nothing. Usually there is an engine hesitation / sputter / misfire when this happens. Also seems to happen mostly when I'm cruising and more frequently when pulling my camper. I initially suspected some kind of flapper valve in the air intake system but can find nothing there. Then I though maybe something from the GT unit but that doesn't seem to make sense. So now I'm thinking maybe it's something from the engine exhaust brake system. Has anyone out there experienced such a noise? I'm concerned it could eventually lead to serious failure but if I can't find the source can't do anything till it blows.