Manual trans? It's likely the ABS module. The manual trans ABS modules have a couple settings that can't be fully disabled in VCDS, just set to "normal." The ABS sees the high torque "low boost" scenario exiting a tight corner as a threat and tells the ECU to cut power. Watch your boost gauge; the car should cut boost each time it breaks up. You can test this by pulling the ABS fuse then going for a lap. An Auto-X course with a couple real tight turns should also reproduce this issue. With the fuse pulled this break up should not occur.
It sounds *exactly* like what was happening to me too and I feel lends some validity to the shop suggestion! - now that I think back, the car would stumble/hesitate and not build any boost glancing down at the boost gauge when it occurred. I'd open the wheel and let off the gas, give it more throttle and all would be well. Might explain the odd "hydraulic sound" i was hearing, if this is caused by ABS. Do you remember offhand which VCDS/obdeleven module or setting this is?? I'm going to dig into this and report back if I cannot find it. If I need to pull my ABS fuse, this should be neat.