You most likely have a dual action fuel pump which is supposed to generate more vacuum that if the wiper motor was connected straight to the intake manifold...
Try connecting your wiper motor directly to the intake manifold to see if that changes things..Remember to plug the vacuum port on the fuel pump..
If none of that helps, try sending your motor to Rob Ficken.
www.wiperman.com He rebuilt my motor and did a teriffic job. It wipes like never before..
