98 quattro emissions failure

[quattro chris]

hi all, my 2.8 quattro has just failed emissions and smells like its running on ethanol. Garage want to charge me £500 plus to replace boths lambda sensors and both cats, is it possible to narrow the fault down and if its cat, replace with decat pipes

Any advice is greatly appreciated, as this is my first audi. i have to mention she has done 250K, but still runs sweet as a sugar

 

[aragorn]

Decat pipes wont pass an MOT.

Vagcom scan will tell you if the lambdas are working.

I suspect that they are, and the problem lies with the cats as the cars probably running its original cats and 12 years and 250k miles will likely have seen them to deaths door.

If your lambda figure is near 1.0, and the CO around 0.5% then the lambdas are likely fine, and the cats are simply defective.