asanal wrote on Nov 18^th, 2010 at 7:29pm:

CoolP, "I always load my flight plans in the INS only" Do you mean you enter coordinates of flight plans waypoints into INS? Sanal

This just means that only the INS unit "knows" about my flight plan. FSX doesn't know and therefor no GPS unit does.
As Mark pointed out, there are some ways to load your plans into the INS or to enter them waypoint after waypoint.
Loading stuff into FSX always means that the default GPS module and gauge now sees your data. But as there is no connection between them and the 707 (as I said before, you can search the panel.cfg for any GPS entry, there is none), guidance can't happen.

You are saying that it DOES happen and my only assumption would be that the Doppler gauge uses the FSX loaded data then.
The INS units can't do this by design and as I always go INS-only, I can't reproduce your described 707 behavior.