i have a similar problem...
standard my car ran 11psi with a Autometer boost guage...
I noticed that same prob, when boost kicks 2500-3000rpm it feels as if its loosing it, and at about 5k its comes back.. didnt register on the boost guage but..
Hooked up a Turbosmart dual stage boost controller.. and it does the same thing but worse.. 90% of the time it does it... sometime it works and hammers..
Im thinking it has somehting to do with the fuel cut as im running 13-14psi boost...
Bu then again.. it was doin it before i strapped the boost controller..
R32 gts-t run 10-11psi stock
My car was also converted to manual from auto... but didnt have the problem after the conversion..