Update, 

I quintuple checked the float tab level is about 14+ mm from the lid. I also checked the fuel levels and they seem about the same. I also took off the suction chamber again thinking the jet needle might have been shifted back some, and it did a little so I went ahead and fixed it. Still having the same issue, the colortune mixture shows rich with the mixture screw all the way up, but I lose power under load.

Thanks!

Should the vent lines on the floats be capped off or left open?

Mine are connected via hoses to the air filter housing. I wouldn't leave them open if it were mine. Fuel could overflow or spill out with aggressive driving. But they can not vent if capped off. What type air cleaner are you using?

Best image I could find with my phone.

 Does the colortune change color (turn blue) as you try to accelerate and lose power?

I've got these kind of Air filters on, so no vent lines. 

I have run my SUs without a tube attached for 15+ years. Do not plug them. 

On 5/31/2020 at 12:25 PM, Mark Maras said:

 Does the colortune change color (turn blue) as you try to accelerate and lose power?

Looks like that's the issue. Finally got around to taking another look and the rear carb has blue throughout the range, but the front runs rich at idle and blue on throttle. Not really sure why the two are behaving differently, but at least now it's drivable.

 

Thanks!

I'm going to assume the floats are set correctly and the mixture screws are about 2 1/2 turns down, correct me if I'm wrong. Try lifting both carb pistons and drop them at the same time. They should be very difficult to lift but should drop at a much faster rate. Both should feel the same when you lift them and they should land at the same time or nearly so. Compare the piston heights when it's idling, accelerating and at about 3000 rpms.