okay noticed today while driving past a fence and a wall a slight sputtering sound underneath my car ... well i filled up gas and got on it and now im hearing a whirling sound when the RPMs drop coming from passenger side right under engine or by headers....

now i unbolted my y-pipe to change an o2 sensor couple days ago.. think the flange could just be leaking and need to be tightened?


what else could this sound be...?

 

Yup sounds exactly like a leak. I have a slight one on the pipe I have existing where my cat. used to and it sounds like a hissing/sputtering sound when I drive past something on the passenger side under throttle. Gotta get that fixed it drives me crazy. Can I ask why you unbolted the Y to change the O2 sensor? I thought you could do it with the pipe installed on the car.

 

it was my o2 on my passenger header and u could but was much easier just to unbolt the pipe with my headers... also turned out the leak was my first primary on my header the bolts had loosened... tightened them and it was fine... it was funny though cause the sound echoed into my y-pipe