Tim's Jag

My 2.7 ltr diesel has developed an intermittent turbo problem. The engine management light comes on occasionally and sometimes I get a "restricted performance" message on the display in the dash. When this happens the turbo doesn't run and the power output is very low. I understand that this is a fairly common problem so if any member can help me I would be very grateful. I am looking to find a specialist who can fix the problem at a reasonable price. Many thanks.