The Pro System 950 is really only 830cfm. Took a lot of tuning to even get it to idle nicely. I don't know what they do with their calibration. I had to drill 4/ .106 holes in the throttle plates just to get it to idle on the T slots. The Proform was really close out of the box 4/.080 holes idles nice. WOT both are good. I put the emulsion basically like the old school holleys are on both carbs. IFRs down low.