Just finished installing Megan Racing test pipes and that hissing is killing me :/ This is a problem with the y pipe right? just want to make sure i know what it is cause i dont have an exhaust leak and ive heard that the hissing can occur from going catless.
also im trying to decide between z1 cai, stillen gen 3s, and admin intakes. if anyone has any input, performance wise, they'd like to give me i would greatly appreciate it!

Test pipes are a big contributing factor to the hiss/rasp. Resonated ones, like ART pipes, will have less. Is the rest of your exhaust stock? I had rasp with ART pipes and stock exhaust. Got the Motordyne catback and it smoothed out greatly.

Check out SOHO Motorsports new intake. I think I've decided on it. Great price and gains.
https://sohomotorsports.com/products...take-kit-69-mm

All intakes listed will provide good gains. Just depends if you're getting a tune or not. Stillen and Z1 you won't need one although it would be a good idea. Admin 3" intakes will need one and SOHO says they recommend it.

Nik, owner of SOHO, is a great guy and I was recently e-tuned by him on UpRev.

Stock exhaust?

I just have a muffler delete but I am planning on getting a full exhaust system soon
Might look into those SOHO intakes but my tune is gonna have to come a little later so maybe a different intake would be better so i can run without a tune for a bit

I'm on the same boat. When I go under the car I can actually hear some of the hissing coming from the Y pipe itself. It seems to come from the flex pipe. Am I correct?

I have test pipes on my 350z also so I'm familiar with the hissing and have learned to live with it. But in the G37 a lot of it seems to come from the OEM Y pipe.