Engine runs rough on incline/idle

If the engine runs poorly on a hill, I would suspect the fuel pump is sucking air. If you try with a full tank, does the same thing occur?

I have owned 2 of these now. A 1990 and a 1996. They all seem to idle rougher for some reason when parked on an incline and in park. I found by putting on the Emergency brake and alowing the vehicle to rest on the emergency brake, then shifting it to Park, takes the load off of the park gear and idle smooths out. I think its just small design flaw in these cars. Drove the 1990 208,000 miles, idled rough every time on an incline, no harm done.