A tiny click click click can be air coming from between the reg and the air tube.
Either use some soapy water, or some gun oil and run it around the joint between the two. It may also be worth testing the joint between the reg and the action of the rifle, but it is more often the tube to reg. It the leak is there, then it is usually just a new O ring that is needed, not an expensive or difficult job.
If air is coming from the vent hole in the reg, then that's just a quick rebuild with new O rings in the reg and on the tube and action (best do them all at the same time).
"I'm your huckleberry, that's just my game"