All I can add is I always noticed my 1989 shortbox was all over the road during normal driving ,regular sized tires, no lift, no drop etc ....my 89 had an EVO pump on it (not sure if it was original to the truck ) but not electrically connected with any wires etc ...that pump started to whine REALLY bad ...I ended up putting a 1992 Camaro pump on it. It IMMEDIATELY felt better going down the road , no wandering or correcting necessary going down the road or interstate , no correcting after hitting bumps etc etc....again my EVO pump did not have the electrical connection connected to it ...so i attributed it all to that EVO pump ....FWIW .