I have a Mitsubishi lancer 2007 station wagon (CS-2V) with CVT. It has a 4G15 engine. the problem i am facing is that when the car is accelerated with a light foot there is knocking. the knocking goes away if accelerator is pressed in further. A usual suspect is the CAT converter but i checked it and it does not appear to be clogged. I have no intention of getting the CAT removed. Also the knocking is not there if i use high octane fuel. @Xulfiqar if i can get hold of an OBDII sensor, what data should be monitored for the knocking issue?

secondly i have changed the tires from the original 13" rim to 14" rims (have kep the overall diameter as close to original as possible) got the alignment and balancing done as well but the car pulls towards left. have gotten the alignment checked twice but to no avail. what can be the reason?