whistleing sound or whining sounds

Guys! I just put brand new autolite resister sparkplugs on my 94 cavalier rs with the 2.2 liter. I just noticed a whistling sounds or a whining sound,not sure how to describe it,but I can hear it at under 20mph like when driving slow through the walmart parking lot or just down the street. I used to have double platinum sparkplugs in it and to be honest,I dont think its worth it to one who can very easily change them out! I also believe that the platinums or better suck down more gas. But back to the point,Do I have anything to worry about? I'm not sure,but I think a piece of an old spark plug gap fell down in cylinder#4 I can use any help on this! I can't complain about the gas mileage though.