Revs Drop off Options

[ianb]

Can i have some help here guys?......the revs on my st205 drop off down to zero whenever i brake hard or change gear and more often than not the car ends up stalling......even when not in gear if i rev up to 3000 rpm and then release the pedal the revs crash below tick over and then bounce back to tick over again sometimes causing car to stall....its getting quite dangerous now and the car hunts a lot sometimes when waiting at junctions or traffic lights??.....and again goes low enough to cut engine out??.......if i turn my wheel slightly (power steering ) this tends to steady out the revs???......any solutions please?

Ian