Coil Light Keeps Blinking?

Hi all,

I have recently purchased a 1998 Audi A4 1.9 TDI and unfortunately the garage I bought it from had accidently fuelled it up with petrol! They took it to a mechanic who drained the petrol and replaced the deisel filter and also put some injedector fuel with a full tank of diesel. It was then taken to an Audi specialist for diagnosis to check for any further damage, they said the reading said that it was fine and they reset the system.

Now the car drives like a dream, however the coil/glower light(orange light) keeps flashing after about a minute of starting the car. The garage I bought it from say that it will go in about 500 miles or so, its coming on becaues the computer is self diagnosing itself and becaues of the previous traces of petrol is/may still be in the system,

Anyone had similiar experiences or know why this has happened?

Thanks in Advance