Im new to this forum and know very little about the Cooper S.
The Mrshas just bought a JCW
2004 with 80k on the clock and all was fine and pulled hard but now 3 months in its like the car has no boost.
You can hear the supercharger whining but its like there is very little pull.
I have read about bypass valve being an issue could this be hers?
She went to "a specialist" today who advised the CAT could be blocked which i do not believe.
The only other thing we are doing is the usual plugs,leads etc.
Any help would be massively appreciated.