To start, 2013 G37 Journey Coupe, 103k miles. Currently have a P0340 code, came back after clearing it and driving less than 5 miles, making me believe its a cat.

I'm not trying to spend 2k-3k on new cats, if I replace one, I'm replacing both, which is making me lean toward HFC's, specifically the Z1 motorsports ones. I do not want to drive around with codes, that pisses me off a lot, can I get HFC and not have any codes pop up from them? Or would I need to get a tune? Should I get a tune anyway? How much would I be looking at cost wise? I don't know of any good VQ tuners in Arizona, which is where I'm located. Very confused right now, if anyone has gone through this situation please guide me through what you did and what I should do in my situation. First post, sorry if ****ed it up.

 

i ordered oxygen sensor spacers

 

what for? do u have stock cats on or aftermarket?

 

i have aftermarket cats

 

https://www.garlaven.com/products/m1...8aAtSAEALw_wcB

 

Generally aftermarket HFC's shouldn't throw a code if properly designed, and they are 100% safe to run without a tune. The ECM will adjust to the change in airflow etc. If you don't like rasp make sure you get a resonated option, and please excuse me if that's old news to you.

You can try an 02 sensor bung extension or canceller like the one linked above but YMMV- at your mileage your OEM cat material may be deteriorating and might be starting to clog up if so. It's very likely the OEM cats on their way out, but could be the 02 sensors or even a leak on the intake side of things (the plastic OEM intake material tends to become brittle and crack over time which can throw a few codes).

 

Hey! Thanks so much for your input. Luckily, the code went away on its own. I'm thinking it's something to due with the weather because I'm in Arizona, it's pretty cold (for us) down here right now, I started it and the code just wasn't there and it hasn't come back, pretty odd. I just bought Z1 Post MAF intake hoses and also got aFe dry drop in's to compliment it. I also haven't cleaned my throttle bodies in two years of ownership, so... yeah... Haha. Since the code popped up, I did a ton of research and know what to do when it comes back, because lets be honest, it probably will. I'm gonna go with the FI resonated hfc's when my cat's go out, paired with my Beluga Axle Back it should sound pretty damn good. Thanks again!