Thats around what a friend of mine got out of his engine fuel wise/lifetime.

Otherwise, start checking all the usuals...

Air leaks, fresh glowplug, fuel and pressure lines for pinholes (or just replace 'em) blocked in-tank or external fuel filter.

I've also got someone running a +4 Nova as you mentioned and it too has nominal compression and pinch, but runs great. They've played with their metallurgy again...