Exhaust leak

[1990 quasar blue]

I finally have the headers on, the RT cats and exhaust welded up, and am ready to head back to the dyno. When the car idles, I hear a very faint tick. To me it sounds like a slight exhaust leak but, the flanges and all the joints look clean. The exhaust guy said if it's making a ticking sound, then it has to be a header flange. My questions are 1. Is the exhaust guy correct? Or could it be a flange at the cats? 2. What's the best way to find a small leak? (I've read of some guys using Sea foam) and 3. Will this screw with my A/FR's or any other dyno data? I've tried tightening the header bolts that I can get to from the top and they are tight. Any help would be appreciated.
TIA,
Mike

[32valvZ]

I would say that the leak could be at the collector (s) OR the flange on one of the heads. Drive it for a while & then look for a black trail of condensation & carbon at the suspected attatching points. When its cold is probably when it will be most pronounced. :cheers:

[1990 quasar blue]

Thanks, you're right. I only hear it when it's cold and even then you really have to listen for it. Unfortunately, all the joints are still spotless.