The O-340 in my RV-9 does exactly the same. Automotive plugs, dual electronic ignition, burns Mogas, and if I want to dawdle, the fuel flow is down around the 15LPH mark at 120KTAS, probably lower, but I don't fly that slow that often. 145KTAS at 8,000 burning 24.2LPH of Mogas is what I plan, and achieve regularly. And that will probably increase to 150KTAS when I tidy up a few draggy items. I was able to put it in the air for well under 100K using the QB kits, a brand-new engine and Dynon package.
The current holder of the CAFE TriAviathon is.....A (very tidy,admittedly) RV-4...250SMPH top speed, 44SMPH stall, and a RoC of 3300FPM.