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Jake...I had my Holley 850 massaged by Jet 2 years ago for my 418W and what I got back was an extremely rich carb from idle to WOT. Just from what I am hearing, it "sounds" like your power valve may be too low in number. Jet put in a 3.5. I swapped it out for a 6.5 since my vacuum at idle was 14". The idle screws were way too rich and the motor would lightly puff black smoke at idle. Mixture screws way too far out. After rejetting from an A/F ratio of 10.5:1 at WOT to 13:1 at WOT, the car made better HP, +35, and less black smoke. Changed my squirters from 35's to 28's, changed power valve to 6.5, changed jetting from 78/87 to 73/75, turned in idle mixture screws from 2 1/2 turns out to 1 full turn. You would think Jet could do a better job of redoing a carb, knowing all the motor specs you give them, better.