exhaust manifold question

[hank]

i've got a '71 cheyenne with a 350 and ramhorn stock manifolds. this week i got new exhaust(dual dynomax turbos, aluminized pipe with an H pipe). all is great, sounds great and i've got more power.

today i got an exhaust leak and it seems to be coming from the passenger side manifold. only happens when i putting my foot into it.

i have a few of questions:

1) is there a gasket there that i could have blown, or is it more likely a crack in my manifold?

2)is it just a coincidence that this happened a couple of days after i got new pipes? or could they have been damaged during installation. the shop i took it to has a great reputation, so i would hope they would have told me if something had happened.

3)has anyone ever heard of installing glass packs BEFORE the mufflers to quiet them down?

help me make her sound as good as she looks again.

thanks for any help.