29 Running Rich at Idle

Not sure if this is inter related with the vacuum tank issue. 
Running 16-17 vacuum at 600rpm

Chasing black soot build up on all 6 plugs. Have added a single copper .0075 wire to main and aux jets. Venturi is flush. Flapper is also flush. Float set for fuel in bowl at 1/8" below and then again at about 3/16  bit below low speed jet as Geoff recommended

No change.

Able to adjust the knurled screw for good idle but after 30 minute run at idle plug inspection still finds black soot.

Is there need to reduce the low speed jet diameter as well?