I was on track at National Day in my RS1800, it has a Superchip and was revving fine right upto 6500 rpm. I was coming down the long straight and the revs were up at about 5500 when suddenly there was a kind of a pop and the revs dropped right off, also straight away there was a lot of noise from the exhaust, possibly 3 times as loud as it was.

The car is not running right and has the following symptons:

1) Very, very loud.
2) Down on power, after 4000 revs there is no go, just loads of noise!
3) Will not rev above 5000 when driving but revs to 6500 when standing.
4) It is very lumpy and blowy when idling.
5) It's using loads of fuel.

I took it to my garage believing I had an exhaust problem, they had it for the whole day, they said that the exhaust system was fine but told me a hose had popped off and they re-fitted it for £50!!! I got the car back but it was still no better.

Since then I have removed the Superchip, disconnected the battery for 1/2 an hour in case it had gone into limp mode, had a fault finding machine on it, no faults found, had an emmissions test, all fine.

The car is still not right and I really want to get to the bottom of this problem so I can sell it. I phoned my local auto electrician and he's convinced I've knackered the CAT, my local mechanic doesn't agree however. I have got a 2nd hand replacement CAT system to go on the car, but I don't want to get it changed over if it's probably not the cause of the problem.

Any ideas, help or opinions appreciated.

Thanks for reading, apologies for the essay.