For me it'd have to be the Altezza 280T
Stay with me on this one: Looks like a normal lexus IS200 with a nice kit, but under the hood is a factory 3S-GE vvti BEAMS and a factory standard guaranteed TOMS Turbo setup. Also has other improvements from TOMS (suspension, wheels etc). This would be a great sleeper car - looks stock, but could own most things on the road.
The 280 stands for 280 ps (at 7600rpm), and when combined with the approx 1300kg weight, lets just say if this car was mine I would be a very happy boy (sigh) >

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