There are three versions of both carbs, pre HP, post HP and Ultra. I have had and used both carbs and both types of the early ones, none of the Ultra. I like the early 9375 non HP for single four foot brake racing They are a two circuit carb. with no power valves originally that works very well on a single four intake foot braking I have loaned my 9375HP out before adding jet extensions to a local racer, he said it work real well out of the box, but it did bog on the hit, I'm sure due to no jet extensions in the rear I have track tested the non HP 8896 with stock jetting compared to a non HP 9375 with stock jetting and the 9375 was faster by around .04 and .3 MPH I have also dyno both carbs, 9375 with stock jetting versus 9375HP with stock jetting and the HP made a little more power, not much, 5 to 8 HP and similar torque in parts of the dyno tests, not all the way from (on every 100 RPM measured) 4000 RPM to 7000 RPM BTW, the stock 9375 are a two circuit carb. with non annular boosters and no power valve, the 9375HP are a three circuit carb. with power valves front and back with standard boosters.