I was driving my car not too long ago, and I was running ~80 and me and my dad noticed an unusual vibration. The car used to be very smooth when running high speeds, but I tried it again today, and >75 i can feel an abnormal amount of vibration, especially when I engaged the throttle(not horrible w/o the throttle). Anybody have any ideas? I would love to figure it out, sorry if the text is too noobish...
02 Z28

 

Tire balancing maybe? Maybe one of the weights fell off the wheels.

 

I'm gonna take it down to the tire shop and have them check the tires, I hope that's what it is.

 

could be a u joint on the way out