^^^ What he said.
Visually, the engine is the same, and with the larger exhaust system it probably wouldn't sound all that different, plus the engine was changed by BMW themselves due to some problems that some batches of the smaller engine had (something to do with nikasil or something?) and this was the reason for the swap, and BMW do have records of this, but that was a risk i was willing to take, and even if i told a new owner about the larger engine, which of course i would do, and anything happened then i wouldn't wish to saddle them with being in trouble over insurance fraud.