noise

[bkwdc]

Periodically, it will sound as if the muffler has fallen off or head pipe came loose on my 300. Is this a pv problem?

[(F5)]

yes, most likely,

but check the header springs

[bkwdc]

For weakness or missing?

[Jakobi]

I'd say more likely to be o-rings. My first set blew out in no time and it sounds like the pipes going to fall off.

Check the alignment of the pipe (not tweaked at header)
Replace o-rings with Viton ones, and use RTV Red high temp silicone on spigot.
Double and triple check the 2 x mounting brackets. I've snapped a couple of top mounts (sheered the rubber off), and also the stock lower mount wore out quiet quickly too. I even snapped the whole tab off the frame once.
Also, some find some rubber sleeving over the springs also reduces the sound of them against the pipe.