There is a lot of controversy. By the letter of the tax code, as written (2004 codes, I am not sure about 2005), you can deduct $2000 *IF* your ST is equipped with a Flexible Fuel engine, which I would assume that the '04 of yours is.
I deducted that amount last year for my 04 ST without issue.
If you consult with a tax advisor, which I recommend, don't be surprised if they tell you different, or that they say the same. Seems even the tax advisors and the IRS can't make sense of the muddy water of this area of the code; some say one thing, others say something different, even in the same organizations.
What does the HRBlock site ask? Turbotax last year had a bunch of questions guaging eligibility, then left it to you to enter a deduction.
TJR