This could be a number of things. In addition to checking your motor mounts, I'd also check the torque on your lug nuts, your tire tread wear, and get your wheel/tire balancing checked. That should be a fairly good start on figuring out what may be wrong.
Sent from the future.
2012 Kona Blue 3.7L V6:
Borla LT headers, O/R h-pipe, Borla S-types, 3.73 gears,
Steeda adjustable UCA w/ mount, BMR LCAs, Airaid CAI,
LCA Relocation brackets, AE driveshaft, GT 80mm TB,
Black 18x9/10 2010 GT500 Wheels w/ Nitto NT555s,
Eibach Sportline Springs/shocks & Koni STR.T Struts