1 - Wheel balance
2 - CV Joints....common problem in S2K.. if it's on WOT then it's most likely CV Joints.

 

you need diff spacers to fix that problem.

evasive has them for sale.

t1-r half shaft spacers. should fix the problem.

 

I have the same issue. I'm taking it by Honda tomorrow morning to check it out. Service guys said it sounded like wheel balance from what I described (which reaffirmed my suspicions). Might or might not get charged for the balance, depending on if they see it as part of my warranty, since I only got the car 3 weeks ago.

 

Rebalance wheels. It takes 10 min or less a wheel. If the problem exists, there is most likely an alignment problem. (check out your rear toe)

 

Honda just told me that 3 of my wheels were out of balance. Not majorly, but enough that it would be causing the vibration issue at 75mph. I would definitely try that first and see if it cures the issue. I plan on testing it to see if its fixed in a little while when I can go get the car.

Good luck!

 

probably your half shafts vibrating. does it always do it? speed related? rpm related? what about coasting in neutral? how long have you had the vibration? how long have you been lowered? rule out a big black vibrator being under the seat ok.