Last nite, was driving home. Only going around 60 - 80kph. Suddenly the car started to somewhat, jerking. I was maintaining throttle, but the engine seemed like, doesn't jerk badly, but it's feels like the exhaust flow is not going well ( don't think it's the muffler, since mine's a straight flow and i didn't utilise my removable silencer ) After a few kms, the probs suddenly went away! Today, I thought the prob was gone. Driving to work for about 3 kms, and then it started again. This time, it was bad! I can still drive the car ( only drove about 20 - 40 kph ) albeit, the car was "burping". At the traffic light, I revved the car slightly to 1500 - 2000 RPMs, and when lift the throttle off, slight popping sounds came out from the exhaust.Note : recently changed to a new 2nd radiator. Prolly the guy who done it forgot to bleed the cooling circuit. Temp went to max, white smoke from exhaust... next day, mechanic re-filled water via the opening the coolant nipple, only then he started filling water and waited until water started to flow nonstop, then closed the nipple and filled the rad water up ( it's bleeding the cooling circuit, rite? ) The current idea is : head gasket needs to be changed, was going to do it this Sat ( since my mech just got married and is having his honeymoon until tomorrow ) Ideas guys? Something went wrong big time in the engine?