Spark plug + coil change -- am I being too sensitive?

[B///MWGuy]

Hi, I've just changed my spark plug and coil for the first time.

I haven't noticed before the change, but I'm noticing a very very faint vibration noise coming from the hood.

However, I do not smell anything unusual, car runs great, I have better acceleration, and my mpg improved.

Should I be worried about this very faint noise? It is difficult to hear, but it sounds like interior vibration -- low pitch sound.

[jandref321]

I ordered plugs and coils but read shortly after ordering that you should only change part of the ignition system at a time. This is so you can rule out certain things if you run into problems. Do you have a code reader? You can get misfires without throwing a CEL. I'd check codes to see if you have any misfires and maybe move the coils around or reinstall the old coils to rule them out. Did you replace the plugs with pregapped plugs or ones that you have to gap? Is it the correct gap?