I have a stock turbo and intercooler piping and when my truck was pulling a car trailer up a hill I could hear the turbo making a fluttering sound. The boost really did not drop it was around 10-15 pounds. But after i unhooked the trailer and drove it and floored it the boost would only go up to 21 and then drop to 0 and then it would start climbing over again the hole time still at full trottle. it used to go up to 24. But when I had the pump turned up more it used to loose boost the same way. So I just turned it down and it was fine holding at 24. The only thing I can figure is the turbo is worn the boots are all good on the piping. The only thing I can see is that the elbow the is attached to the compressor that goes to the first intercooler pipe is that there is a small indentation where a o-ring should be but there was not one does anyone know if there should be one.

 

Yes, there should be a rubber seal there.