Last I read from the US Customs web site, to import a car newer than 25 years you have to go through a registered importer, and there are none for most cars. Generally speaking they only handle expensive cars (Mercedes, Ferrari, etc). There are always exceptions, like the historical law that went into affect a couple of years ago and by which Bill Gates finally got his Porsche 929 after sitting on the docks in San Diego for a decade ...

The only grass-roots import I heard of was for 1994 GTR certification, which I read recently was pulled by the government due to irregularities.