[jhandy]

Dirk-
Reading the first post again, It really sounds like something is loose, because of what you said "by holding the wheel it seems to stop"
If it was a bent wheel, or rotor, or axle....you would not be able to fight it. My wheel spacers shook so strongly if you tried to hold the wheel hard, it would shake your shoulders.
try something simple......jack it up take each tire off, and check the axle nut torque, and put the wheel back on correctly torquing the studs.
I bet its either the axle nut or the wheels. Look for missing lead.

Also you should get the alignment specs and bring them to your shop. Brakecheck can align a porsche, but I doubt that they will know what settings to shoot for.

When I lowered mine, the dealer printed out for me target settings depending on how I wanted to drive it and how fast I wanted to replace the tires.

IIRC the choices he gave me where "factory, street/sport, track"

each choice used the tires progressively more. I chose track, and the car stuck to the road, but I went through two sets of tires in 15000 miles. The camber/toe was so aggressive that it wore out the inner shoulders leaving the outer edge 50% used.

I had it reset to factory values, and drive slower, and use much less rubber.