Any ideas on this faint clicking i'm hearing? It only occurs when moving in gear, in the lower rpms, with light to medium throttle. It started to happen right after the header install. Any ideas?

the header might be loose. try tightening the nuts a little harder, but not too hard. don't break them cause then you're screwed.

My HS did the same thing. I double-checked my torque on everything.

It went away after a short time. My bet is that the flex-pipe on mine was very stiff when I got mine. I think it loosened up after being heated & cooled several times...

Now the resonation at 2500 rpm is another story...

Thanks for the tips, i'll try re-torqueing the bolts. Anyone know the torque specs by an chance?

It may be an exhaust leak coming from the header and block.

I believe it is 37ft-lbs. IIRC.

I had the same problem when I first installed my HS header. I retorqued every bolt and found out that the plug for the aiv hole was lose. That fixed the problem.