You need to check two other things. 1. Does the problem get worse once the truck gets up to temperature or hot? 2. Does the steering get stiff when the drive gets jerky? One way to check is once the truck gets hot, drive very slowly while constantly turning the steering wheel. At that time both problems should be significant. If so, then the boost pump is no good and there should be no need to buy the pressure test kit. The boost pump is the rear piggyback pump connected to the hydraulic pump, however I think it is only available as an assembly. If you need more info, you can reach me at gitpartsatadelphiadotnet.