I have an 06 WRX with 10,000 km and have had a front end shake/vibration
issue for the past 4000 km. The problem seemed to start at the same time my rotors failed/warped at around 6000-7000 km.
My rotors were replaced under warranty but the shake and vibration did not go away. The dealer thought my Bosal exhaust was the problem and that there was not enough flex in the system. I have had 3 Subaru Master techs look at it and say the exhaust is fine and has as much flex as the stock system.
I have had it alligned and a road force balance done. No broken belts, bent wheels etc.
The shaking seems to be there from even low speeds but gets much worse over 100 kmhr and really bad at 130-140. The steering wheel shkes and you can feel a lot of vibration and shaking in the front end and through the whole driveline, pedals, shifter, floor boards, seats, etc.
The motor and tranny mounts seem to have softened up quite a bit and the shaking in the car is more prounounced under throttle, especially when hard on the gas.
The steering wheel also feels a little more chaulky and gravelley then it did, but that could be the RE 92's wearing a little.
There seems to be a lot of shake in the shifter, even more when the AC is on. The axles look fine and there is no strange noises or grinding coming from the car.

My mods are:
AP Stage 3
VF 39
JDM STI top mount
Bosal DP
Bosal 3rd cat elim.
Bosal 3 inch intermed. pipe
Bosal/SPT 2.5 axleback

I have Group N tranny and motor mounts ordered for it and hope that helps reduce a little movement.

Does anyone have any ideas of what could cause this. The Subaru techs and myself are stumped. I'd like to get some ideas before I have Subaru start taking off parts.

Any input at this point would be appreciated.