My passat is no longer mad

[mrlee]

this is what ive had done to mine (130 04 est) much better mpg and goes like fook its est at 150 bhp sounds like you'rs has been done

Question: how would I know if it had been 'chipped' by somebody else before I bought it?

If you have access to VAG-COM you can log the MAF figures. At wide open throttle a 'standard' car will give a pretty well defined value to within a few g/s, a remapped one will read significantly higher.

I don't know off the top of my head what a typical value is, but it's not hard to find.

There's even a calculation to estimate BHP from peak mass air flow, but the relationship isn't linear and the accuracy is highly debatable.

If you don't have access to VAG-COM, then you could get it dyno'd on a rolling road for around £50, but for that you could buy a decent VAG-COM cable and have change.