My suggestion would be to CAREFULLY take a really long screw driver and place the metal end on various parts of the drivers side of the motor such as injectors, valve cover, intake runners, etc. Then place your ear up to the handle. You'll be surprised how much you can hear. Next, compare the sounds you hear on the drivers side to those you hear on the passenger side of the motor. There so much mechanical noise with an engine when you've got the hood up that it's hard to pinpoint noise sources when there's so much going on and sounds bouncing of the panels and concrete floors, the loud and normal tapping of injectors, fans blowing, etc.