is it best to run without a thermostat
 

as above for high performance ej22 lump

No mate.

The job of any thermostat on any engine is to keep the engine UP to temperature, and to get it there quickly. NOT to keep it cool. Once the thermostat opens, it's unlikley to shut if the car is hot and gives little or nothing in the way of stopping coolant flow.

Engines run leaner when hot.

Can't say for a Scoob, but the figures quoted for carburretor cars with a choke, used to be, air to fuel nmixture: 1:4 stone cold, rising to 1:10 hot and 1:32 at running temperature.