For a starter, try http://www.nhtsa.dot.gov/cars/rules/import/gray0006.htm
You'll also need to get the EPA version of the story. This isn't a bad place to start, but in typical Federalese, it leaves more questions unanswered than answered.

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'93 500E
'88 Tyrrell/Cosworth DFZ 017
'95 Ducati 916
'00 Ducati MH900e