Got this merc, 208 chassis, 230K on a t-reg. Will not rev, goes very flat. Its ok on light throttle but open it up a little and it wont rev, it seems to be linked to the supercharger clutch, it comes in and it goes flat with a booming sound in the air filter box, air flow reading doesnt appear to drop off. There was loads of faults, all cleared ok except for the brake light switch, replaced the switch and that fault went away but still wont rev. No faults coming up.

Any ideas people? If ive missed out any info i'll add it or find/measure it as anyone mentions it.