Even though the exhaust gasses are hot, they have already had the oxygen burnt up, so introducing the pre-burnt gas into the cylinder it take the place of fresh intake air limiting the oxygen- fuel ratio. I'm no expert but I don't think the EGR hooks to the turbo at all. I think the wastegate controls the point that the turbo starts boosting, and the the overpressure sensor that is fed by the line coming off the intake near the firewall goes to an switch that opens the bypass valve, limiting boost. So again, I'm new to turbos, but there should be two controlers hooked to the turbo, and the EGR is a seperate system. Any experienced torbo gurus want to jump in?

__________________
'84 300SD veg-oil bliss
'83 300SD veg-oil beater