Hi, Mike; Don't understand the 'friction in the gas pedal'. Quite a few things can cause vibrations at speed. Have the CV joints on the front axles checked. If AWD, check the u-joints on the driveshaft.
The vibration during braking points to the brakes, themselves. Have the rear brakes and wheel bearings checked. If you are experiencing a side to side 'wobble' in the steering wheel when braking, I'd suspect a warped front rotor. If you are feeling a pulsing brake pedal while braking, I'd suspect a warped rear rotor (assuming it has rear disc brakes).

Good luck.