My '04 Mazda 6 recently started making a clicking nose (similar to a noise made when running a stick across a wooden fence quickly). It seems to be coming from the front of the car, and to right of the gas pedal. It is a manaul transmission 2.0 liter 4 cyl. engine. In lower gears the noise only seems to happen in mid RPM's. Once i'm going full speed, 55-75 on highway, the noise is quite dimmed by road noise, but still audible. In the higher gears it only seems to make the noise when pressing the gas to maintain speed. If it step off the gas or floor the gas, the noise subsides.

Any idea of what could be causing this? I've been reading about problems like this and it seems it could be anything from bad gas, need oil change/engine cleaner, to loose valves, etc. Any help is appreciated and also a cost estimate would be helpful.

Thanks!
It doesnt make noise in neutral, so I dont think its the clutch and its not a belt....and no change in noise in turns..only seems to happen with pressing the gas