[IdahoDoug]

Former vehicle developer here for both GM and Lexus. I've experienced loose front wheel bearings that don't wobble except under braking. One easy test is if its most obvious under the light braking you'd experience as you exit a freeway ramp, but under heavier braking you don't feel it.

I have not removed my front rotors yet to know if with your new rotors you have to put new wheel bearings on. If the answer is no and the wheel bearings are untouched then I'd put them at the head of the list as a suspect.

I'd also check your tie rods and all other front end bits by laying on the ground and gripping each tie rod one at a time while someone wobbles the steering wheel quickly back and forth. You'll "feel" the tiny thump or click of a bit of slack this way long before you'd hear it. Easy check for tire/wheel is to jack each tire barely off the ground in turn and have someone spin them. Your eye should easily tell you if either has a wobble by watching the tiny gap from tire to ground. There is normally some - no tire or wheel are perfect - and if there is "some" plus you have slightly loose wheel bearings on a sporty car without overdamped power steering you will feel it. If so, try swapping front to rear tires and see if one of them is "rounder" and diminishes it.

Another random comment is that if a car is supposed to have a slight toe-in on the fronts and instead its perfectly straight ahead then it is easy to get what you describe. Just a faint tension on the tire patches toward one another will damp that slight wobble from a nonperfect rim, or wheel bearings that are on the loose end, or other real life variations, etc. That's probably why someone mentioned alignment. I don't know the 944's specs but I am taking mine in next week as I recently put new struts in and new tires on, so this is the right time. Good luck and post up what you find.