my holley 650 Vacuum secondary carb runs:

Rich during cruise
Rich during neutral idle
Rich during WOT

lean during In-gear idle
lean during part throttle take off
lean during part throttle acceleration


and whenever I try to correct the highway richness, it runs too lean during part throttle acceleration.

And whenever I try lowering the "Neutral richness" it wants to die in gear from being too lean.

#66 jets in front, 6.5" PV.
#72 Jets in rear, no PV.
front idle mixture screws only.

 

Let me add its not "vacuum sensitive".

That is, if im cruising @ 18" of Hg, and i step into the throttle a little bit, it begins to run lean immediatelly, around 15" of Hg.

Same thing with off the line and "town cruise"
if im cruising @ 13" of Hg, and i step into a just a bit more- 11" of Hg, it begins to lean out and stutter.

Bringing up the power valve doesnt help because even on the highway from 18-15" of vacuum acceleration it still runs so lean it stutters. and it KEEPS stuttering, until I get near WOT. but during a flat out cruise, no acceleration just cruise, it runs richer than heck....

so the jets are too rich, and the powervalve wont help. its somthing else, some other curcuit i dont know about thats clogged up.