Speakers in the headrest of my newly purchased 91 miata are full of static and come in and out- any suggestions?

sounds like they're blown - not uncommon, seek out some replacement speakers, can find them from $60 - $300 depending on the kind of quality you're looking for at places similar to Fry's Electronics (or even Amazon.com, ebay etc..) just make sure the size of the speaker fits the headrest.

i had a pair of 2" tweeters put in each of mine.

unzip the head rest and replace the speakers with a pair of 3" or 4" speakers.It means you have to make a timber backing board but 2 x 25 watt speakers give great sound