When I am letting my car idle I am hearing a medium loud puff come out of the exhaust pretty regularly. I don't really know how to describe it, my friend seems to think it's the prologue to backfiring, but I think he's wrong.
Uhh, for lack of a better example it sounds like this:
mmmmmPUMmmPUMmmmmPUMmm
Now I feel stupid x2 haha.
It is an 87 Turbo II, I figure the exhaust is somewhat clogged up, I'm gutting my cats soon, so we'll see what that does for it. Anyone have any other ideas?

 

I had that "puffing" sound before I gutted my main cat.

I also had a noticable hiss whenever I would open my throttle.

I'm pretty sure it's your cat.

 

Some cars exhibit a slight misfire at idle. Not much to worry about. You can change your idle mix to compensate.

 

Mine does this too during warm up. I do not have any cats ( straght pipes). Once it warms up it idles fine.

 

There either clogged or there is leaking fuel and igniting in the exhaust. I have had a rotor go out on me and basically not igniting fuel and they would explode in the exhaust or not explode but ignite.

 

I am having the same problem, and was advised that it was the cat.
I also got a sound coming from the center of my exhaust, about center of my car, like a little piece of rock jumping around.
anyone else have this problem?

 

My car also does this. It's an 91 n/a. At idle its like mmmmmmmPOPmmmmmPOPPOPmmmm...etc

 

I think this is normal. Mine does it too ('91 NA).

 

Thankyou for doing that hahaha.
Also I just changed from 10w-30 to 20w-50 and the car is noticeably slower. It has lost its pickup and go. I also got the LSD fluid changed out, fuel system flushed, and the transmission fluid too.

 

mine does that too at idle when cold, after it warms up, its completely fine.