That's almost always a rotating assembly problem. New tires doesn't mean it's not a tire. Young people drive the crap out of cars and brake hard at the last minute. If it's wet, they can heat up a rotor and warp it easy. It the tires are new, take it back and have them check for an out of round, broken belt or warped wheel. Pulse under braking is a rotor. I did have one Cavalier that the half shaft would walk out a little and caused a vibration under accel-the opposite side could vibrate under decel. I'd bet it's a tire/rim problem---it is the day after big party night too.
Doug
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[This message was edited by PonchoV8]
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