I wanted to get test pipes but heard all the rasp and drone that they can produce so I went with these resonated ones. The quality seems really good, I just put them on the other day and they are LOUD. Might also be because I have no muffler hehe but with an exhaust these will sound great. No CEL came on which was why I ordered these in the first place. Overall I'm really happy with these.

Used on my 04 G35 - I wanted to avoid seeing a CEL everyday, these did the trick. They also help with rasp, I used these along with an ISR y-pipe and Tanabe exhaust to build a really nice sounding system on my coupe. Unfortunately I had them installed along with the rest of my exhaust system The quality of all of the pcs are top notch, it all fit together extremely nice with gaskets included - my mechanic was happy he did not have to make any adjustments, it all bolted up well.

Fitted these to my Stagea 350rx Four. The pipes bolted up, clearing the steering and prop shafts. There was a drama with one of the nuts on the left three bolt flange, it's partly blocked by the upper O2 port, which needs the bung to be removed. Didn't encounter this on the right side. Has reduced the drone and rasp through the rev range. Looks to be well made with no major lips or joins on the inside. It does sit a bit lower under the car. Overall, veey good, but not perfect.