troubleshooting exhaust leak???

[1badv10]

installed a new set of headers last week. but now have the annoying tick of an exhaust leak /forums/images/graemlins/angryfire.gif /forums/images/graemlins/angryfire.gifi had to weld an o2 sensor bung in along with welding on new collector flanges to the existing pipe(i am not the best at welding)when i run my hands around the pipe during a cold start i dont feel any air leaks.. and being that its ticking makes me think that its at the head... any thoughts on how i can narrow this down? /forums/images/graemlins/dunno.gif i have checked and rechecked the header bolts and they are all tight, also i am using "percey's" (sp) reusable header gaskets that i used for a month or two with the old headers /forums/images/graemlins/thinking.gifhmmm maybe i just answered my own question??? but any ideas would be great /forums/images/graemlins/waytogo.gifthanks guys!!