I love my GT500 replicas. They have always vibrated some since day one, and my stock ones don't. I'm going I try and get them rebalanced next time I put them on and see if it helps.
Did you take off the little clips that hold on the brake rotors? Aftermarket wheels don't always clear those clips, and will cause the car to feel like the tires are not balanced. If you haven't removed those, try taking them off and see if that helps.
2008 Mustang GT Deluxe, Black, Manual Transmission, Black Cloth Interior
Show: Katzkin Leather Interior, Matte Black 10" Stripes, NXT Step Performance Axlebacks, Pypes M80 Mufflers (mid mounted), CDC Sequential Tail Lights, 14" Shorty Antenna, Ford OEM Plenum Cover, Ford Semigloss Black Painted Valve Covers, Leather Wrapped OEM Steering Wheel
Go: Airaid Race CAI, BAMA Tune, J&M Lower Control Arms, JLT Oil Separator
Coming Soon: Motive 4.10 gears