Can anyone help?

We have an Autotrail Motorhome. When we are driving above 3000 rpm the turbo light comes on and the engine cuts out, revs go down, we slacken off on accelerator and the engine starts
again. We think the problem might be the Turbo Sensor Valve. Is so where can we get detailed engine diagram or workshop manual so that we can locate this sensor and hopefully replace it?

Thanks