Trouble driving uphill on 1991 Pontiac Trans Sport

1991 Pontiac Transport Minivan slow down when driving up hill. The greater hill, the slow the vehcile travels.

Asked by for the 1991 Pontiac Trans Sport
Checking fuel pressure would be a good first step. If you can road test your 1991 Pontiac Trans Sport with a fuel pressure gauge attached so you can see it you can then monitor fuel pressure while driving. Fuel pressure should be steady while driving up hill. If the fuel pressure drops you may have a problem with the fuel pick up inside the fuel tank.
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transmision starts to stran and sutter