I have a boost issue that happens about one out of every five times and I'm not sure where to begin looking for the source of the problem. Here is my setup:

Stock twins set for 0.70 BAR (~10 PSI) and 64% wastegate duty for both turbos.

I accelerate hard through first gear verifying a normal boost pattern. I shift to second and accelerate hard. The boost builds up quickly, but begins to taper off causing an increasingly sluggish feel to the point where RPM's almost stop increasing. In other words I'm going nowhere. If I take my foot off the accelerator for a second or two, then accelerate hard again, boost builds up and exhibits a normal pattern.

Could this be a tuning or mechanical issue?

 

I may be way off base on this one, but on the stock turbos IIRC there is a plastic box that holds vaccuum to aid in some type of turbo control. Again, IIRC it has a one way check valve on it, so if that is installed wrong or if it went bad, or if there's a leak, you might have a problem like this. Sorry I can't provide any more details from memory but that might at least be something worth checking into.

 

Most people in the 3rd gen forum, and Tom at RotaryRX here in Albuquerque agree that it is the check value. Thanks.

 

Its a mech. problem Check the vaccum chamber for cracks but its mostlikely the little green check valves.