[Moritz55]

Hi Matt ... I have a 770cfm Holley on a Roush 427SR (even though the valve cover is 427R !!).. my Carb is identical to yours.. 2 mixture screws in the front (passenger & driver side) .. none in back... That's Normal.. nothing to worry about.

Note .. I have a solid rod linkage so my pedal moves precisely when the carb accelerator moves.. The suggestion to ensure your Return Spring is Stiff Enough to always return the carb accelerator is a geat suggestion.

Additionally as several already mentioned if you have a Mechanical Advance clean the springs and levers. I just replaced my MSD Disty Cap & Rotor as they were in terrible shape. 21k+ miles on them and never replaced by the prior owner! In the process I cleaned the Mechanical Vacuum springs/arms under the Disty Cap as a preventative measure ....

Good luck and hang in there..