I don't think it hurt to put it in
I was wondering if I should add some pollyfill to fibergalss speaker pods??
no, vent it into the carpet if you can. I assume these are kickpanels?
if in the doors, try using aperiodic enclosures to resrict backwaves into the door, then "seal" the door using roll on sound deadener to completley eliminate back wave cancellations.
are these kicks or door speakers?
yes they are kickpanels,
do you mean port them into the carpet?
not a port, more like a hole. usually we use a 2" hole saw over here. mashed into the carpet, it acts as kind of a aperiodic enclosure, restricting the back wave, but not trapping it. I hear that a vast majority of cases it sounds better. I havent heard any setups first sealed then unsealed myself, so I cant give you an a/b comparison with concrete detail, but the accepted method is to vent out, rather than to compensate with polyfill.
that being said, I built a set of sealed kickpanels the first tiem I ever built some. I had some major resonance problems, and polyfill was reccommended as a potential solution. It helped, but I had to stuff the CRAP out of each box (close to a pound per box!) to get any noticible improvement.
my next set were vented, and vastly better. because of the venting alone? probbaly not. but I cant imagine it hurting, considering the universal acceptance of venting and my own successes/failures.