1993 Miata turbo, high fuel consumption 10 mpg.?

The Miata is a 1993 with 32,500 miles and a t25 turbo. After re installing the rebuilt turbo mileage went to10 mpg from 34 mpg. Replaced plugs, wires, coil pack, O2 sensor.Rough start ups sometimes misfire until it warms, very black smoke, flat spot before boost and quick de acceleration with backfire in exhaust. Acts like fuel starvation but running extremely rich. I am assuming pressure regulator but could be a combination of things. Also, over size radiator, engine
never really warms except at idle. Any suggestions?

Are you driving fast or accelerating fast?
Check tire pressure.
Make sure air filter is good.

Sounds like you need new valves to me.