I'd check your MAP sensor - I had similar problems and after that got changed everything was fine.
I wouldn't have guessed it at the time though and thought it was more to do with the remap or TB. GGR were the ones who diagnosed and sorted the issue - chaps there are far brainier than me

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Moondust Silver '07 - naked - rear tinted privacy glass, Janspeed manifold, sports cat, rear box, Ramair induction kit & catcam cams. GGR 175+ custom remap.
Performance

magazine July 09
179bhp @ fly & 200Nm torque (before remap)