Just curious what could it be if when you let off the gas with the boost at 20 or even 10 psi it sounds like it is "farting" but only when you are at boost and letting off as it falls to zero?
its very possible the fitting for the hpop has come apart again. there has been another revision to the repair with a new part, its practically a threaded pipe that should fix it permanently this time. The new set up is about 3 months old. it really looks like a good setup this time. i hope you get your truck fixed in an accurate and timely matter