Just changed the spark plugs on my 2006 scion tc. Since then there has been a buzzing noise coming from the spark plugs/coil pack. When I rev up the car high it goes away but every time I start my car it buzzes again. No check engine light. Anyone have any idea why this would be happening? I used the correct iridium spark plugs gapped to specifications so it cant be that. All of the coils were working perfectly before with no buzzing and after I changed the spark plugs it started buzzing from all 4 coils.