It's just a wing I got second hand from a guy who imported a Honda CRX which had that stuck on the back of it! Looks about the right size for a GTR but it absolutely dwarfed the little CRX - looked ridiculous!
The M3 was not without its problems. It's had an engine swap to try and sort out an oil leak, which was later discovered to be the oil pressure switch leaking! But anyway the swap only cost a few hundred quid (+ his old engine), and the new one has some fairly vicious cams + headwork which give it a fair bit of poke