Nah, the computer doest adjust to the operating temperature, the sensor has fixed resistance values. If your car was running cold (depending how cold) then the computer simply increases fuel mixture to increase rpm to prevent rough running and stalling when the block is cold. Since you have fixed the thermostat, the engine will heat up to the correct temp. Yes it will increase fuel efficentcy if yer engine is runnin at the correct temp.
EB1 3.9L MPI Falcon Wagon with converted T5 / Pacemaker & 2.5" Redback sports exhaust / 2" lowered blocks at the rear, Kings lows up front / ED Tickford Head and Cam / K&N panel filter with XH intake Snorkel / Full EL Fairmont interior with woodgrain
89 EA1 3.9L TBI Falcon Sedan with 3 speed auto / currently being upgraded...