The first thing I would do is heat them up. You can do this in an oven (use some good heat resistant gloves) and then try to work the piston up and down. Chances are good that it will free right up. The same for the throttle, heat and gently try to work the throttle; as it heats up it will break free and rotate fine. Now use some fuel or thin oil to lubricate the moving surfaces. I have freed up stuck throttles with just a heat gun on the assembly while gently applying pressure to the moving parts.