dashboard light (car with spanner through it)?

I have a vauxhall combo van 2002 and im having problems with the turbo when i seem to get to like 80/90 on mway and revs get to about 3500 the turbo knocks its self off and you can feel it trying to kick back in.
Over the last few months its got worse and now the light is on all the time and sometimes the turbo fails all together which mean van wount go over like 10mph in 1st gear, im also worried about having an accident when im pulling out of a junction just incase it stops working please can anyone shed some light? cheers :) if anyone can help email me at mark28481athayhoell.comm