Mercedes Sprinter turbo problem
 

I have Mercedes Sprinter 211 CDI 2001 year. It works very well, but I have one problem. When I start driving it goes very well, but when you drive it for while on 2200-2800 RPM it shuts down turbo. Then i just turn off and then turn on car, and it's goes normaly with turbo. And if I drive again on same RPM ratio, it hapends again. I changed turbo and chechked all vacuums, but everything is normal? Does EGR have any to do with this, and do you know what I can do?