Originally Posted by Moparrbust
The first few years of the SL55's had the 74mm TB and made 496bhp..............then M-B upgraded in 07(I believe) to 80mm TB and it jumped to 517bhp.
The first SL55 Production year 2002 had the 80mm TB without a Bypass in the IC. In 2003 they changed it to the Bypass System with a 74mm TB, mainly because of lower fuel consumption. The new SL55 07/08 with 517bhp again uses a 80mm TB.