Originally Posted by 03SSLE

Maybe back pressure from the clogged cat caused a portion of the manifold to head gasket to blow? Use a piece of hose and listen around the manifold and see if you can pinpoint where the ticking sound is coming from.

Originally Posted by DRuben

Might be the flange on the beginning of the DP, I got my dp installed at a shop and they never got it to seal correctly and I have a small amount of air coming through. Pop the hood and put your hand over the flange and pull the throttle on the throttle body and feel for air... A good indication of an exhaust leak is the smell in the engine bay

Originally Posted by Mike 00LS

Well it wouldn't be an exhaust leak - they hiss, not tick. Check around your intake for anything - if it was lifter tick like on the 31 and 3400s it would be doing it when cold and not under load, then stop once it warms up, so I wouldn't think it would be your lifters.

Originally Posted by The_Maniac

I just had a thought. You can hear it on the back of the engine. Check your spark plugs! Engine cold, just take your hand and see if any wiggle. My 3100 had a plug that kept coming loose (eventually the threads stripped, I think this was due to the first time I changed plugs, previous owner had one over torqued in there). Each time it came loose, I heard a weird ticking noise (oddly, never had a performance problem, engine still ran tip-top). Usually I could see the plug wire move frantically when I'd rev the engine which is what led me to the loose plug (on a 3800, that may not happen so much).
I eventually had to use a Sav-a-Thread heli-coil kit and did it all with the head on the block.
Other thing to look for would be anything that is loose back there or disconnected.

Originally Posted by DRuben

My exhaust leak certainly sounds like a ticking sound. Cant really hear it unless im next to someone or in an enclosed area. You know that clapping sound open manifolds make, an exhaust leak will be almost the same but escaping through the leaking area.

Originally Posted by Jomao_o

My exhaust leak definitely ticks, real annoying.

Originally Posted by 01 Monte SS

If you find the leak make sure you use a lot of high temp rtv if possible! I used soo much on headers and cat back but there's no leaks so I can say it works

After having a leak where my headers bolt up to my cat back it had a sound like a tick more so than a hiss. But I put a gasket in there and a bunch of rtv and it's now sealed and the tick is gone

Originally Posted by The_Maniac

I have faith this issue will be found. I'm hoping it turns out to be something super simple (that the worst part is finding it).

Originally Posted by zjerry

Mine was leaking at EGR tube ..

Originally Posted by Franks 03SS

thats what i was thinking too, its just hard to reach my hand down there and feel for a leak, and it gets hot really quick! what kind of hose would i use, just a small rubber hose?

Originally Posted by lougreen03

My buddies truck had a weird tick and it was the belt tensioner. It sounded just like a lifter and he only found it because he took it to a mechanic that had seen it before.

Originally Posted by 03SSLE

If you have any laying around heater hose works well, but even a piece of 3/8" fuel line or an old garden hose will do the trick.