Just to clear this up for you all!

Every ECU will work on every rs turbo including hearts and diamonds!!

No mods needed unless you are putting a S1 Fuelling ECU on a S2 then the TPS needs rewiring or it will not work.

The knock sensor does NOT need to be plugged in and only came fitted to the later S2's, many of us unplug it because after so many years its got oversensitive and ends up retarding your timing cos it thinks your detonating when your not!

This i know form my own experience