Dan mate, an sps2 will NOT ALTER PERFORMANCE AT ALL in the way you are thinking, and there is no "fitting" involved.
please look at this link:
http://www.revotechnik.com/products/sps2.aspx
In basic terms: An SPS2 is a SWITCH.
It allows you to turn your revo ON or OFF (ie back to standard).
It allows you to disable the ECU, to stop anyone starting your engine.
It allows you to chose a SLIGHTLY different revo code, depending on the fuel type you use - ie if you put in supermarket fuel, select 95ron setting. If you use optimax (or similar), you select 98ron.
Thats it. It does NOT give you more power. To "install" it you put it into the socket below your ashtray in the centre console - and you then unplug it once you have changed the setting you wanted to.
Check the "for sale" forum for any that might be on offer. Otherwise you will need to buy a new one from Revo.