Exhaust acoustics

[radzoule]

I am confident I don't have any manifold leaks and my car is not pinking, yet at idle (have an undulating idle due to cam) and when I plant the throttle (esp) at lower RPMs there is a definite "rasping" or "chuffing" sound from the manifolds/cat area which diappears when you back off and are not under load. TBH it sounds a little agricultural to me.

I have ACT de-cat manifolds, but listening with a hose at idle the culprit seems to be the cat.

Does anyone else understand what I'm talking about?!

I wondered whether wrapping the whole lot up in exhaust tape might dull down the sound a little. Anyone got any thoughts?

[Mad Mitch]

Sounds like you may have a restricted flow through the cat. Could be partially blocked.

[Cider Andy]

I had an identical sound, but accompanied with a slight misfire as I opened the throttle and a few degrees rise in engine temperature. It was a pig to trace and turned out to be either the distributor cap or rotor arm (I replaced both). Sound gone, temperature back to normal. I would have sworn blind it was an exhaust leak, but it cured it.