[ultraflo]

I was under the impression that the stockers were referred to as manifolds? (Even though they do look like a poor excuse for headers)

Anyhow, that's not important...
Have someone get about a 2-3 foot length of 1/4-3/8 i.d. rubber hose and stick one end in your ear and the other around the header flange area on where the suspect leak is coming from. This will allow you to determine where EXACTLY the leak is coming from. Be careful not to blow-out your ear drum in the process...

If it's coming from where the header mounts to the cylinder head, then you're do for a new gasket set.

However, I have seen them develop leaks on the flange where it bolts to the h-pipe. Rust wreaks havoc in this area! Either the studs themselves rust in half or the flange rusts and gets weak, distorts, and tick tick tick you have an exhaust leak!

I have fixed a few of these and sometimes you can temporarily get away with heating up the nut with a torch and giving it a couple cranks. If that doesn't work, then the studs need to be replaced and you can add washers to compensate for a semi-distorted flange. If the flange on the h-pipe is shot, cut a new one in half and weld it back into place. If the flange on the header is bad, you need new headers!!

Hope I could help! I work in a muffler shop and see this from time to time...