That one Brett is not for S54 and I think a Simpsons alternate using a Mota cooler would try to do the same thing but you have problem with space ESP if you have a/c rad
OPTIONS to replace OEM are Turner, Fluidyne, Bimmerworld, HPF
All are a little bit different but I think the BIMMERWORLD one is best and cheapest and direct replacement, longer and double pass cooler.
http://store.bimmerworld.com/bimmerw...ler-p1517.aspx
CA do sell one but it's nearly £1000
the HPF one comes with or without the ducting which on M3 is not required so $100 cheaper.