If your rocker pin cover plate has 5 bolts securing it, then you have an ST4 head. The belts for sale on this page fit this head style. ST4 heads were used after 2000 on all 748 and S4 models.
They're not cheap, but the ST4/ST4S and all Post-2000 748/S4 requires these OEM belts.
These belts will fit all ST4/ST4S and Post 2000 748/S4 models (which have ST4 Heads). Belt purchases are non-returnable. OEM Part # 73710101A, which supercedes part # 73740103B