I was looking Megan Racing M-Spec II for end muffler and Y-Pipe. However, there are many issues that their products crack a lot and people said their products are crap. IMO, the sound is good on G35 (not really loud)but dont know about HP gains after Custom settings (Y-Pipe Mid Pipe Mufflers) Mufflers are 300ish for two and 150 for Y-Pipe.

Other mufflers that I thought about is HKS mufflers or Apexi N1 mufflers
I do not like loud exhaust but a bit more than the stock one. HKS and N1 mufflers are about 300~350ish and I need two of them so..like under 700 bucks.

Should I purchase HKS or Apexi mufflers?

 

HKS and Apexi are much higher quality parts but also twice the price. If you have the money, go with the HKS carbon Ti but many of the Megan parts I have seen are pretty decent quality so you would probably be fine.