bleed your system

Changing the rotors almost always fixes the problem. (Hope you did the pads, too.) So I wonder whether the rotors are the problem.

Do you feel the pulse in the steering wheel as well as the pedal? That would mean the front brakes are where the problem is; if you only feel it in the pedal, that would indicate rear brakes. There has been a rear brake 'resonance' issue in the past, which can be fixed with shims on the pads....but your dealer should know this. There's been a TSB out on this for a while.

Get each wheel in the air (put the car in neutral for front wheels, parking brake on, chock the rear wheels) and give each a spin. They should rotate without the pads hitting a high spot on the rotors. If you hear the 'chiff' of pads hitting a high spot, then you've got a warped rotor. I believe OEM rotors are warranted.

In my RWD Volvos, pulsing under braking could also be caused by worn torque rod bushings; it wouldn't surprise me that a worn suspension bushing in the FWD cars could also cause a similar problem. (I haven't experienced it yet, so I don't know about this.)

If your rotors ARE warped, you might consider slotted or drilled rotors as replacements as they run cooler.
--
David \\ (98 S70 T5SE Black, misc mods (mostly lighting), red calipers) (92 940GLE)

Did they replace the rear rotors? Warped rear rotors typically
cause this sort of vibration (based on past posting hear).

I'd suspect a sticking front caliper piston as they usually do that after driving the car a bit, heating up the brakes. When it happens, the effected wheel will be VERY hot and discolor the rotor. If the effected wheel is elevated off the ground with a sticking caliper, that wheel won't turn freely as it should.