I’ve found a bad engine mount over the passenger front wheel i’m replacing (why they had to put the 5th nut holding the mount underneath the mount instead of on top like the rest, i’ll never know. drilling that out and replacing with a bolt and nut on top to fix that and going to slap an engineer). There’s no wheel balance issues or wobbly wheels when up on the lift. recently replaced my spark plugs, could it be a misfire that causes this when the engine is being pushed past 3K rpms?
The vehicle is OBDII compliant. If there were a misfire the Check Engine light would be on with a code indicating a misfire.
I would first try swapping the front tires with the rears to see if the vibration moves with the tires.
If that has no effect, then looking deeper into steering/suspension components would be next in order.
Tester
Where do you feel the shake? More in the seat or more in the steering wheel? Will it change if you come off the throttle? Or get on the throttle? When is the last time the steering and suspension components were all inspected?