C36 HP at 280bhp?

Dear Listers,

Just finished reading Road & Track "Bahnstormers" {featuring Alpina B-12, Ruf , and AMG C36) in 1993, and Automobile magaizine featuring George Karcher doing a report on the AMG C36 in 1994, they both report that the horsepower ratings were 280 bhp (EUROPEAN). What are the changes between the european car and the north american car to reduce horsepower by 12? The C36 even in it's final iteration did not produce 280 bhp. Is it possible to add or subtract some equipment on the early north american C36's to produce that kind of horsepower?

Thanks