When I decelerate I hear a loud chirping noise from under the hood. I have long tube headers and I've capped off the air tubes. What could it be?

 

mine was the AC belt replaced it with a Auto Zone GatorBack for $17

 

Also could be the tensioner pully, mine is doing the same thing right now, going to replace it here very soon.

 

I removed the AC belt completely. It sounded a little quieter but it might be my imagination but I still hear the chirping noise when I decelerate, especially around 2000-1500 rpm. It kind of sounds like its coming from the back of the motor.

 

tranny?

For some reason I first thought that problem might have something to do with the transmission fluid, or perhaps a belt/clutch issue.

 

I and many ls1 owners have had to deal with this noise. For me and many others it has been the top belt. And from my experiance you have to get the gm belt or else it will still chirp -squeek-. I have gone through 2 aftermarket belts before going with the gm belt. It is a bit more expensive but it does remove the annoying chirping. You are better ordering the belt online, you can get it cheaper then at your nearest gm dealership -its been my experiance. The upper belt number is #12569527, gmpartsdirect.com - sdpc2000.com