S52's were for the US market, do you mean the S54's (The E46 M?) Power in the S50 is the same as the E36 but they had to lower it slightly (325bhp) for the S54 due to the exhaust routing (officially, unofficially its suspected that it was due to the bearing shell failures that the E46's were plagued with)
Thought about a different exhaust , but not overly keen on how the ACS looks on the Coupe - mine have been tweaked internally anyway and sound a bit more aggressive than the standard backboxes...