2003 Ford Ranger 4.0L Engine P0046, P0068, P2196, P2198 Fault Codes - After Coolant Leak Repair

I own a 2003 Ford Ranger with a 4.0L engine. The vehicle previously had a coolant leak, which I repaired by replacing the thermostat housing and water outlet. After refilling the cooling system and allowing it to warm up for 20–25 minutes, the engine ran smoothly at idle with normal temperature readings—no leaks were observed. The next day, when I attempted to drive it, the vehicle began sputtering as soon as I pressed the accelerator. At idle, it exhibited hunting behavior. When accelerating without load, it reached around 300-3000 rpm for a few seconds before dropping by nearly 1000 rpm and then resumed stuttering and hunting. My friend used his scan tool to check the system. While driving at low speeds with light throttle, the engine ran smoothly—idle was very stable. After parking and leaving it idling, it suddenly began hunting again. It would run up to 3000 rpm, stay smooth for a few seconds, then stutter, return to smooth operation briefly, and repeat the cycle. At times, it would shut off unexpectedly. The diagnostic tool revealed the following fault codes: - P0046: Evaporative emissions system vent control malfunction - P0068: MAP/MAF throttle position correlation issue - P2196: O2 sensor stuck in rich condition — Bank 1, Sensor 1 - P2198: O2 sensor stuck in rich condition — Bank 2, Sensor 1 The vehicle ran normally before the coolant leak repair. I am now concerned about whether the repair process or a secondary issue caused these new codes. Any insights into possible root causes or troubleshooting steps would be greatly appreciated.