2008 Mazda 5 P0791 Error: Causes, Symptoms, and Connection to Engine Temperature Drop

Hi, I own a 2008 Mazda 5 and recently my check engine light has activated with Diagnostic Trouble Code (DTC) P0791. In addition to the warning light, I've noticed unusual driving behavior — the vehicle feels sluggish, especially when accelerating, as if there's insufficient power. Furthermore, during highway driving, the engine temperature drops from around 90°C to 58°C, which is significantly below normal operating levels. I’ve read that a malfunctioning thermostat stuck in open position could cause such a drop in engine temperature. I'm wondering: Could this thermostat issue be directly related to the P0791 code? And if so, would it also explain the poor acceleration and driving performance? Any insights or suggestions on how to diagnose or fix both issues would be greatly appreciated. Best regards, Arie