For low end response the YB is a poor engine both geometrically (bore and stroke) and mechanically (Inertia of components) I'm afraid.
The huge and heavy flywheel doesn't help, nor does the very heavy bottom end.
The thing is just hugely over engineered for low states of tune and will never feel like a modern lightweight 4 pot that falls to pieces at 350ftlb of torque.

Advancing the cams to shift the engines efficiency lower can help significantly if your willing to run more boost up the top to overcome the VE drop or indeed don't care about BHP figures but ultimately, a responsive revy little engine she isn't.

That said, without driving your car I couldn't comment on how yours actually performs, and the usual responsiveness problem is normally exasperated significantly by bad states of tune, specifically very rich mixtures, poor cam timing and spark timing issues. Not a lot else I can add without access to the car itself.