Cheers mate, Closed Loop entails a chip from MSD and the fitting of a Lambda Sensor into your downpipe, usually a Bosch LS02 one, I think it's something like whilst the engine is below 4psi and above 70deg temps it will run in Lambda 1, basically perfect fuelling, you do need an L8 ECU for the conversion though, full link here:

http://www.motorsport-developments.c...losedloop.html

I did 912 miles at the weekend in my saph and it AVERAGED 30+mpg! This included all the stop starting in traffic and endless miles sat around the 100mph+ mark, and all the higher speeds too!