Mine would rattle at idle and that crap was loud. I got tired of hearing it and people looking at me like wtf is that lol.. I pulled the heat shield out and walla!! oh, I tried bending it so I wouldnt loose it but got tired of messing with it..

 

That SARD hfc is fake. You can see the label is wrong. Also as far as power loss is concerned, top secret did a test on there circuit R34 and they only lost 5hp with the sard cat. Well worth it, it passed emmissions and lost only 5hp! Okay in my book.

 

thanks everyone but its all solved now. went to a shop, put in on a lift, and sure enough it was the O2 sensor hitting against the body.
i guess when i climbed under the car myself, i just couldnt see it.

 

Megan did a terrible job when placing the o/2 bung on its resonated test pipe. I solved this issue with a small hammer. Never heard it again. Glad you were able to solve the issue with out handing out a good ol passionate A$$ whoppin

 

wrap your test pipe in heat wrap, or bend the heatshield, problem solved

 

well actually, my O2 sensor is not on the test pipe, but on the long pipe right before the muffler. and still, the resonation/vibration that the Megan test pipe created, was enough to vibrate the whole exhaust so that th eO2 sensor was hitting the body.
btw, what the mechanic at the shop did, was bang/bend (with a hammer) the bottom of the body upwards a bit, so that created enough clearance for the O2 sensor to vibrate freely in midair all it wants