i have two o2 sensors before the cat and one after. i am not sure, but it doesn't seem like that would be a big issue if i just kept the third one on the right side and had nothing on the left side.
as of right now my exhaust is set up like this: stock y-pipe into high-flow cat, then into 4 in. magnaflow muffler and 4 in. pipe out the right side before rear tire.
im thinking my idea of a 4 in. might have been overkill. sounds really good, but i think performance would be better with true dual 3 in. anyone with more knowledge please correct me if i am wrong.