I have a 2003 g35c 6MT, I have a R2C CAI, 5/16 iso plenum spacer and a magnaflow exhaust (2.5" diam) I'm getting ready to do an uprev tune in the spring and want to put on MD ART pipes for sure. However I've been also thinking of doing the MD XYZ pipe w/ resonator. My concern is I don't want it super loud so the straight pipe is out and I want to cut down on gas smell is the HFC version essential for that? Also how will the ART pipe perform with the stock ypipe and magnaflow vs the XYZ?

 

I have the xo2 exhaust and it had a decent volume that wasn't too loud but better than stcok. I had the ART Pipes V1 and you can here it from a mile away. The ART pipes are very loud. I'm not sure how they would be coupled with the setup you have but if you don't want your car super loud be careful with the ART pipes. I loved mine when I first got them but I ended up taking them off because of the volume. Sounds great but I'm getting too old for that amount of loudness. I will sell them on here once I get enough posts. I got a lot of compliment on the sound though. Good luck.

 

I have similar mods on an 05 sedan; R2C, MD 5/16 spacer, and a MD VQ exhaust with a resonated XYZ. At the time of this vid I also had ART pipes but sold them because it was a little too loud for me. Here's a dyno vid with the ARTs.