I had similar problems when I put the supposed plug & play Simota intake on, but after talking to them they admitted that some cars require a 'settling in period' or sometimes remapping. I'd done about 2,000 miles with it on, and with the engine cutting out when using full throttle, so I told them the 'settling in period' was rubbish and I'd like a refund.
I think pilchardthecat had a similar issue with his.
Never heard of this happening with the Gruppe-M one though.