[iwant3000gt!]

fobos34, опять же 3si.org
The monster of the family and the reason why the 3000GT & Stealth is well known, the VR4 surpasses the rest in multiple aspects. Powered by a well built 3.0 L DOHC 24-valve, twin-turbocharged, twin-intercooled V6, the VR4 produced either 300 BHP at 6000 RPM and 307 lb-ft. of torque at 4500 RPM (10 pounds/square inch of boost in the 1991 to 1993 models), or 320 BHP at 6000 RPM and 315 lb-ft. of torque at 2500 RPM (12 pounds/square inch of boost in the 1994 to 1999 VR4s). To compensate for the lost power in the 1991 to 1993 era, (because of the lower boost), a modification called the "Free Boost Modification" was made to increase the first generation VR-4 boost from 10 pounds/square inch of boost to 12 pounds/square inch of boost. This would successfully make the 3000GT VR-4 first generation make equal power to the second and third generation 3000GT VR-4.

Судя по этим данным 300 л.с. снимали с давлением 10psi=0,69 бар, а 320 12psi=0,83 бар.
Раличаются они только давлением, чтоб это компенисровать америкосы что-то сделали, что не ясно. Ясно одно, нужно поднять давление и получить свои 320.
На счет визуальных различий не в курсе.