So I just installed my berk hfc's yesterday on my 03 g35 coupe automatic and there was almost no change in the exhaust note and also couldn't really feel a difference in hp. My flex is busted on my y pipe could this cause the problem?

 

You didnt notice a hp change, because there isnt one. Unless you have a very senestive butt dyno, you will not notice 5hp difference.

 

So what about the exhaust note is that something that develops over time?

 

After 20k miles you'll notice rasp when your HFC's break, but not really unless you change the exhaust bud.

 

Oh ok thanks for the help