Buying secondhand - sounds like a dump-valve is fitted.
Been away from Mini for a couple of years (used to have a pepper white MCS R53 from late 2003).
We've been looking at a couple of R56's and the one that's favourite sounds like it's got a dump valve fitted to it by a previous owner. Doesn't really look the sort of car that someone would fit one to but nonetheless, the noise is very apparent and on comparison to another same age MCS, the "p'tessss" is virtually none existent on the that one.
My question is, any way of easily removing said dump valve (I know nothing of such things) or could it be something else (problem?) that's causing the noise?