Differences.
higher compression pistons and a different set of cams (more lift & duration)
Different exhaust valves
Titanium Con Rods & 45/50 Termi system with chip to match.
You can fit the higher comp pistons in a bip £££'s
I'm waiting for my Bip-SPS conversion to be setup on the dyno, then I can let you know how much more power it gives.
But,
I got the parts V. cheap.
I was having the topend rebuilt anyway
I fitted vernier pulleys had the cam timing done
I'm retaining my 45mm system
The chip's being mapped on the dyno.
SPS dynochart on sigma's site
http://www.sigmaperformance.com/dyno1lbig.jpg Bip V SPS Chart
http://www.sigmaperformance.com/dyno2-3hp-big.jpg The article
http://www.sigmaperformance.com/748spstech.htm [Edited on 8-3-2005 by Mr_S]