where did you get the straight pipes? can I do it on only one side?

 

I don't believe you could just replace one side with a straight pipe. You would have troubles with different levels of back pressure I believe on each side causing possible issues (I might be wrong). You can get straight pipes at a local exhaust/muffler shop. Make sure you measure the inside and outside diameter of the piping to make sure it fits properly. I haven't take a look under a 2.8 but if it is the same set up as the 2.7T you might be able to even cut the cats off at the downpipes, drop the back exhaust and put in a straight pipe where the cat use to be. Weld the exhaust and you should be good to go. I am sure you can get this all done at a muffler shop.

 

just out of curiosity, using the same logic wouldn't replacing just one stock CAT, with a different brand also cause different levels of back pressure?

I haven't completely decided on using a straight pipe. If I decide to return the CAT I got online, there would be a 20% restocking fee and I would lose the shipping cost I paid, and also the cost to ship it back. This would be about $100.

To put a straight pipe, I'm assuming each would cost about $60, besides labor. May be $200? Not sure.

Now if I really have to replace both CATS, and O2 sensors, which I'm not changing, then I'd definitely go for the straight pipes.

Also if you know, do I have to replace my O2 sensors, I only got a code for the passenger side CAT. I'm positive it's not the sensor, because as mentioned the cat was rattling and car losing lots of power, but I really have no idea how to know if the sensor is bad. Going to a dealer is not an option, neither is buying a vag-com, for several reasons!

 

I believe if you replaced it even with an aftermarket car they would both hold back pressure at the same location. If you had a straight pipe and cat the back pressure would start at different points. Causing possible problems with reving/power to the car when you need it ( pulling out ect ). Ehh I knew they would prob try to charge a restocking fee. I would possible just take the charge or attempt to sell the cat on ebay or the forums. This is a common fault and shouldn't be hard to sell. With the o2 sensor I would honestly worry about the first problem at hand getting the cat code and misfires to go away. None of this is being caused by the o2 sensor and possible could be caused by your current problem.