I've got a 2026cc mild stroker with Webers that was configured to run cool and not necessarily blow the doors off of anything. So, in theory, my mileage should be about the same as yours.
On typical twisty and hilly country roads, where there's a lot of shifting, I average 20-23 mpg. On a highway where I can stay in top gear for long stretches, though, the mileage jumps up to 26-7 mpg. Generally, your results will depend a lot on where and how you drive.
In slow speed stop and go, where I need to dice it up with traffic from stoplight to stoplight, I'm usually down to 20 mpg.
If you have a .89 top gear and 'average' sized tires - 185/60, say - you should be doing around 60 mph at 3000 rpm with a 4.12 r&p and around 64 mph with a 3.88. Measure your speed with a gps, though, as many of our Chinese repop speedos can be off quite a bit. The one in my VS is high by about 10 per cent at highway speeds.