mk4 gti de cat probs

[btk]

Ive recently had the cat took off my mk4 gti 8v and had a full stainless system fitted. Since fitting the car has run like a bag of sh!t keep cutting out no power at all, the fuel consumption has gone though the roof as well. Ive had it checked by my local vw garage and they said the mk4 gti will never run right without the cat. Is this correct?

[topher]

'fraid so mate, unless you use a standalone management (?) the ECU will be getting erroneous readings and you're fuelling will be all c*cked up.
I got my wallet out and bought a high flow CAT made by Milltek, there are about 20% of the cells as a normal CAT and you can see right through it, but the lamda sensor goes in and runs sweet as a nut, fairly decent power gains too.

[topher]

Have a gander at this

http://www.millteksport.com//hiflow.sports.cats.cells.cfm