My turbos were converted to non-sequential recently. Unfortunately there seems to be a problem with their operation. At WOT (2nd or 3rd gear) the turbos begin to build boost around 4500 rpm. Around 5 psi a loud whoosh sound can be heard followed quickly by a chshhh sound (very similar to the blow off valve). The sounds continue in quick succession until around 5500 rpm then completely stop, allowing the turbos to make full boost. At half or three fourths throttle the problem is the same, but continues through the rest of the powerband (the sounds don't stop).

Could the blowoff valve be intermittently activating releasing pressure? I've checked for any other source of leaking but I can't find anything. All unused vacuum nipples are capped, and everything is tightened down. I believe the sounds are distinct, but am unable to verify it. This problem is causing boost to build too slowly because it is being vented somewhere. What seems strange to me is that at WOT, the sounds stop, and the turbos achieve full boost (10 or 15 psi) without a problem.

The non-sequential conversion consisted of removal of the turbo control actuator (but not the gate). Removal of all solenoids, except for a dedicated aftermarket wastegate solenoid. Removal of the y-pipe butterfly, actuator, and pre-charge valve. Removal of all other unecessary intake butterflies. Everything removed has been blocked off. Any help or ideas would be greatly appreciated because I really don't know where to go from here.