Good to see the old thread alive again.
a) My particular calculation does not include the tax stuff, because I never got that tax break.
b) Checking the new configs is fun for me, I don't know if it will be in my favor or not (pricewise usually not). Sometimes though, like when they cancelled my silver color, or this new range and performance "unlock", I see things I like.
Can you elaborate how it’s possbile not to get the federal tax credit? Did you not pay any federal taxes?