You're referring to the M3 built for use in the ALMS series - which was fitted with the 400hp V-8 from the M-5 to be able to compete with 996's and Corvettes, etc (the 6 cylinder E46 M3 was not as competitive as BMW had hoped). This is actually an M Coupe with 380 hp (rumored to be i6), and is much lighter than the M-3, and the std. M coupe.