when i nail my cossie through the gears at about 5000rpm-6000rpm i hit what feels like some kind of boost limiter but if i slowly acelerate it will go past theese revs no problem any ideas only had the car 6 months its runnig 11 psi no chip as of yet

 

I have encountered a similar problem with my Saph, but once I get to about 5000 rpm it will not go any further so have to change geaqr or drop off the power, not sure as to what it could be?

 

I had also this problem.
One of the connectors on the ignition coil was all rusted, i cleaned it and the problem was gone.

 

i will jive that a bash cheers!!!!!!