I have an Apexi WS catback exhaust on my '96. When I was under the car to replace an O2 sensor(one on cat), I heard this hissing sound, like something was leaking from the bpipe part of the Apexi exhaust. I swapped out the Cattman ypipe to the stock ypipe a few times, and it seem like the hissing/leaking sound was louder when I had the Cattman ypipe on oppose to the stock ypipe. I put my hands over the whole bpipe area carefully to feel if there was any air leaking out, I didn't feel any. What gives?

 

I have the same exact setup and I have the hissing sound. I've taken it to an exhaust shop and they didn't find a leak. I guess it's normal for this setup to make a hissing sound.

 

Glad I'm not the only one. If it's normal, then I'm not worry. Thanks.

 

Don't have the catback, but I get a hissing from my Y. Looked it over my self several times then took it into an exhaust shop. No problem could be found. I still think I have a leak, but nothing more I can do

 

How about your gaskets?

 

Nope. Noise is coming only from the bpipe part of the exhaust. I checked the near the gasket and the ypipe, no hiss from there.