I have recently installed an Akrapovic EVO exhaust to my GTR. The exhaust system is as follows;
a. AMS downpipe (non catted)
b. Akrapovic midpipe with resonators
c. Akrapovic catback with carbon tips

It sounds great but with some drone noise inside cabin at 3,500 RPM. I am looking for ways to minimize the drone such as insulating piping among other things. I have heard that using (Cobb) catted mid pipes will eliminate drone noise. I want to know any drawback if I decide to go with catted midpipes. For example; how long will it take for any of the catalytic to clog? Any loss on horsepower? Is Cobb the best choice?
Thanks, Anriel01

 

Any feedback on Cobb catted midpipe?

 

On any car going from uncatted to even high flow cats will result in lost of power.. The cats create more backpressure and depending on how good it flows will determine the HP you will loose. It will also hinder the sound of your exhaust. i dont know too mucho about the noise you are experiencing. I've never had a problem with an aftermarket exhaust.

I have a question for you. How hard and time consuming was installing the downpipes. Or how much did you pay. Can you replace just from the y-pipe and back to pass smog or do you have to change the downpipe back to stock too? I am about to purchase the whole exhaust system and intakes and get tuned to unleash my GTR's real potential