Y pipe or Test pipes??
 

What would you purchase for your next exhaust mod? I will be upgrading either my cats or y pipe. I'm not sure what to buy. I have a V35 G35x De. I heard normal race/performance y pipe won't clear our transfer case and only VHR any vhr 370z G37 ypipe will fit. Is this true? I have an oem exhaust. Which I'll be upgrading in parts instead of going the expense catback route. Most catbacks are just mid pipe with resonater and muffler anyway (not true cat--back). Not worth it imo better to do my own exhaust. I'm either of these mods looking for power but trying to avoid too much rasp. I know both of these mods will make the oem exhaust note louder.

Exhaust systems! (be aware)
 

Quality aftermarket exhaust manufactures spend hundreds of hours testing their systems to get the best sound and the largest return in WHP and torque! Any mod you do to your OEM exhaust will give you nothing but major rasp! There is so much restriction in those factory cats replacing them with HFC's (or test pipes) is like putting 3 lbs. of dog poop in a 1 lb. can, it's overwhelmed causing the above mentioned rasp! Aftermarket y-pipes offer zero gains! There are two types of exhaust systems, the y-back is just that. A true dual begins at the cats with at least 2.5" pipe thru resonators and mufflers before exiting. Sadly some manufactures and many member here will use the words "Cat Back" when that's not really what they're selling or referring to!
Gary

High end systems are tuned for gains and note, piecing together a system or bending your own pipes is a crap shoot, most shops have no way to measure scavenging and note is a guessing game of which resonator and muffler to use. You truly do get what you pay for with an exhaust system and piecing together random parts will not get you the performance gains and note of an ENGINEERED system.

That said, replacing cats will net you gains, replacing a y-pipe will change the exhaust note.