Shit Gas Mileage

This always leaves me stumped. How do you manage to keep it under 2k? Mine does like 3k+ on the highway in 5th. Also, I find that if I shift lower than about 2200rpm, the engine will shudder and refuse to accelerate. This is with an undersquare “torquey” KA lol, how can you shift before 2k in an SR? Maybe my car isn’t running right, I dunno…