The strongest production 4 sold in the US (I think) was the 300HP Lotus 2.2L Turbo in the Esprit - which was wickedly fast.
I was pleased to see a vote for the MR2 turbo motor (I used to own). Only 200HP stock but 200Lb/ft and easily tunable to 300+ HP and possible to tune past 450 HP!
The S2000 motor is just unreal though- 240 HP from a N/A 2L that hits 9000RPM!
Dan

1999 Amazon Green SVT Contour (#554/2760)
Stock SVT Duratec V6 with:
Intake- K&N filter/75mm MAF meter
Exhaust- MSDS Y-pipe/Bassani catback
Durability-Ford "dual mode" damper, Mobil 1/K&N oil filter
179.2 FWHP at 6900 RPM