You don't need a pinion snubber with Caltracs because the bars prevent axle windup. I run the Hotchkis springs and didn't have a pinion snubber for a while, but put one on to help prevent axle wind up. I do feel like it was beneficial. Depending on how you drive your car, you may be OK without one, but I do a fair amount of hard standing starts at the autocross and at Moparty when I drag race and speed stop. I've also modified my pinion snubber so there's only about 3/4-1" of clearance before it contacts the floor.
