GTech Performance Meter
 

Ideally the old school black model made in the 1990s, that looks like a radar detector.

Simlar to this:

http://www.funkystyling.co.uk/gtech/images/gtechpro.jpg

Any other device working on a similar principle (potentiometer as the car doesnt support OBD2) considered too.

G TECH PRO performance meter on eBay, also, Other Car Tuning, Car Tuning Styling, Cars, Parts Vehicles (end time 07-Feb-09 12:30:34 GMT)

I had one many years ago, was a good bit of FUN kit,lent it a mate and i swear he sold it with his car.