Injector Noise

I replaced my sparkplugs a couple weekends ago. Ever since then, I can hear my injectors "clicking" -- from inside the car.

My mechanic says it has probably always been there and Im just now noticing it since I am paying closer attention to new noises. (LONG story...car stolen and Insurance company will leave the estimate open for me in case I find anything wrong with the engine.)

Any ideas? I was afraid I did something when I changed out the plugs. I know the noise hasnt always been there. I am normally very conscious of noises...

Ok, for whatever reason...hearing it again from someone else that it is normal makes me feel better! lol