I used 034 motorsports 02 spacer and had no CEL (p0420) for about 5000 miles. The only time I have a problem is when I run over 90mph, I then get a 02 Temp. code. Your rear 02 might be too much out of the air stream. Try a diffrent spacer! The only other things I can think of is the flex pipe cracked, Cat almost completly clogged.....

 

yeah the cat is still under warranty so im not that worried so i will keep you guys posted. thanks for all the help. im under warranty until like 8 months from now so i may not do it till then because im in school and such. but when i do i will let yall know. i just switched to only one short drilled spacer to see what that does and then if that doesnt work i will go back to the 2 again and then 3 maybe until this upcoming summer

 

i would get that cat swapped quick if u are under warranty still. Im still saying its your cat and those non foulers arent going to work. It might rid the problem for a little while but eventually it will show up again. If i had the choice i woulda swapped my cat first thing! u lose alot of gas mileage running around with that code!

 

Agree but if he doesn't go with a factory cat, he is still going to have the same problem! Our cats are designed to show low effeciant when it goes below 5% which is very narrow! Spacers work! Like I said, I've been driving on my spacer for more than 5000 miles with no problems. There are also guys out there that had their spacers on for more than 10000 miles with no problems. Even guys with HFC's use spacers with no problems. I'm only using a spacer to buy time because $1200-1600 for a cat is a hard bullet to swallow, among other things just to keep these kinda cars running!

 

my gas mileage is about 30 - 35 mpg so my mileage is great. i cant fork out 1200 for a new Audi catalytic converter due to the fact that i also have to pay tuition. and yes i know i can get a different type of cat but it will most likely throw the same code. spacers work