Were the tires balanced correctly? I would take it back to the shop that installed the tires and have them check that they are balanced. Improperly balanced tires will cause vibrations at high speeds, and is probably what is causing your issues.
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2014 Mustang GT 6R80, Procharger Stage 2 D1SC, BBK 85mm TB, Boss IM, Sai Li fuel system. Circle D 3C, 1-7/8" Kooks Long Tubes w/Offroad X Pipe, Lethal Over-Axle Pipes, Corsa Quad Axle-Back, Eibach Pro System Plus, BMR K member, Shaftmasters DS, Forgestar CF-5 Wheels and Nitto NT05 tires. Lund Tuned
Lots of suspension goodies and some other stuff I can't remember.