4-speed automatic tuned to 141 kW (192 PS; 157 hp)
where are you getting that info? The Japanese Spec RX-8 with 4port engine is 210HP at crank.
Secondly, the auto-8 is by no means a "slow" car, its designed as a Grand Tourer so while its not the fastest sports car in its league but its definitely one of the most funnest.