I have an 04 g35 coupe, had it for a little over a year with no issues mechanically.
a few days ago I noticed a fluttering noise but couldn't tell exactly where it was coming from, got up under the car and it doesnt seem to be coming from any of the exhaust piping. popped the hood and it sounds like its coming from the belt area. The noise is pretty loud while the car is warming up but then seems to quiet down, I also hear it sometimes when accelerating with RPMs around 2000-3500. Any help will be appreciated.

mod list:
motordyne 5/16 plenum spacer
Injen cold air intake
berk high flow cats
megan racing y pipe
topspeed y-back exhaust system

 

How long has it been since you changed out the belts? Check them for wear, cracked/missing ribs are the biggest signs you need to replace them.

 

havent changed out the belts since i got car a little over a year ago but they look fine. Yesterday i found that my cold air intake tube had come loose at one of the connections and there was an opening, vacuum leak, but I popped it back in its slot and clamped the coupler back over it but the noise is still there

 

Could be a bad pulley. Personally I'd drop it off at my mechanic just for a diagnosis. Any mechanic should have a stethoscope to pinpoint the noise.

 

Found it with my buddy! Idler pulley has a bad bearing. Thank ya