Hi there, not long ago a friend of mine was inspecting the spark plug on my car.The engine was hot when he did this. When reinstalling one of the plug however it did not fit snug and tight and instead I believe it might have rounded the engine block where its suppose to go. Recently I noticed when I try to increase endine speed suddenly the car starts to vibrate including the gas pedal and i car hear 'POP' noises from the exhaust.It really effects the performance because instead of going faster it goes slower until I let up on a gas. It only happens when I try to increase the speed quickly and it fine when I floor it. Where do you think the problem lies.