I had my 125 upgraded to 150. A Caterham specialist will be able to upgrade the ECU for you, no need for a new unit. The 150 has the loverly throttle bodies, cams, valve springs, tensioner, coolant hose, wiring adapter and injectors, plus the remap. The 140 kit replaced the 150 kit in 2011, but is actually a better drive, but lost the throttle bodies and gained the lightened flywheel (well worth it). Power wise they are the same, but the 140 apparently have better torque. Caterham still does the 140 kit https://caterhamparts.co.uk/other/4817-engine-upgrade-pack-sigma-125-to-140bhp-supersport.html?search_query=140+&results=37 If you have a 270 Sigma, you can get the 310 kit. Never driven a Premier Power Sigma upgrade, but a lot of good words have been said/written about them.