update following dealer visit:
i went in with the notion that the mount was making the noise, seeing as how the noise wasn't occuring until after i put the mount in.
the checked what i had done, and everything seemed to be tight and in tip-top shape in terms of proper install.
we checked around that area to see what could be the culprit, and we came upon the front sway bar bushings. we don't know for sure, but it seems like they could be the cause of the noise.
this explanation makes more sense than the mount, seeing as how the sound doesn't happen on every take off from a stop, and i'm pretty sure that if the mount was loose enough to rattle, i'd definitely feel it (and have some other, more serious probelms).
final thought ... the motor mount stiffened things, i think, to the point that on take off, the bushings are slapping against the frame of the car. i've had my rear bushings replaced under warranty, but are there any types of problems with the front ones? i asked the service guy and he printed up a list of all the recalls for the mazdaspeeds, and no luck there. i think the solution is gonna be to "band-aid" the problem (even though i'd like to just eliminate the problem), and by that i mean put some insulating-type material along where the bushings run to reduce (if not eliminate) the noise they could be making.
any thoughts/comments on my conclusion would be appreciated.
on a side note ... i hear a weird swaying sound coming from the rear portion of my car at all times moving. i have an apex dp and custom catback (with reused stock hangers), so could this sound be all of my exhaust piping moving? no banging in this case - just a mysterious swaying sound. i thought it could be the seats, but it can't be seeing as how right when i come to a sudden halt the sound continues for a couple seconds instead of stopping immidately (which, if the problem were the seats, the sound would cease very quickly).
thanks for reading my damn-long post.
drew.