TT is correctly limiting your deduction; You can't take the full amount. IRS on why you get no higher deduction:
https://www.irs.gov/uac/sales-tax-deduction-option "Taxpayers also may add to the table amount any sales taxes paid on:
A motor vehicle, but only up to the amount of tax paid at the general sales tax rate ...
For example, the State of Washington has a motor vehicle sales tax of 0.3 percent in addition to the state and local sales tax. A Washington state resident who purchased a new car could add the tax paid at the general sales tax rate to the table amount, but not the 0.3 percent motor vehicle sales tax paid."
