Lexus IS200 Misfire after Coolant Loss and overheating P0300 P0301 P0302 P2248

This IS200 has a misfire and the car is losing coolant. The misfire was on cylinder 3 and the coil on cylinder 3 was replaced but the misfire returned and seems to be affecting cylinder 1 and 2 now. A sniff test was performed to rule out the head gasket and it failed so has most likely failed. The error codes are P0300 P0301 and P0302 which relate to the misfire on cylinders 1 and 2, and P2248 - Oxygen Sensor Reference Voltage Performance (for A/F sensor) (Bank 2 Sensor 1).