The OBDII trouble code P1121 is due to your throttle position sensor signal being lower than expected by your ECU. Problems that arise from this OBDII...
Battery registration is an electronic service procedure that tells a vehicle’s battery-management system that a new 12-volt battery has been installed.
Coil on plug ignition technology has definitely accelerated the quality of spark in engines since the early 2000's and it's definitely not slowing anytime...