The HPS's on my 09 dust a lot more then the Ceramic's. I don't drive the Spec near as much as I do the wagon. To me the HPS's dust a lot more.
OP what your discribing is caused by the cheap pads not shedding the dust. The dust build's up on the rotor and causes the wheel to shimmy under braking.
It's been covered here for years.
The easy fix is Hawk or better pads.
Other recomendation, buy from the guy's here. You help them out, and you know what your getting.
Then have a good shop install them and ask them if they can have rotors surfaced not just turned.
174,000+ miles, 5/20/12 new ej257 short block, 8/20/11 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. Also CHECK YOUR OIL, these cars use it.