So playing around with the hesitation when slamming on the throttle, I have found that using choke stops this, and it has a smooth transition. However, it pops on deceleration with the choke pulled. The exhaust is turning a nice blue as well. Doesn't the choke add more fuel, and restrict the airflow? That means it is making it even more rich than the 42/142...
It's not a conventional choke with a butterfly that restricts airflow, but an enriching circuit. It still adds fuel to the mix.
Your description sounds like it's lean (choke helps .. bluing pipes and pop on decel). What color are the plugs?
Could be just a bad transition from the pilots to the mains, playing with the shims might cure that. Like maybe it's a bit too lean, so add a shim? Not sure where you're at with shims now. Or, it's just too lean on the pilot altogether.
Any chance the jets have just gotten dirty? 42/142 should be plenty rich.