Weird noise coming from under dash?

[jasonhirt23]

I have a 2-3 second humming noise approximately every 30 seconds or so coming from under my dash. It started after I did fixed some problems....I changed my spark plugs.....tightened my plenum gas lines.....and changed my oil. I never heard the sound before I did these procedures and now I hear it everyday, every time I drive the car. I believe it stops after a few minutes I think cause after about 10-20 minutes, I'm stopped at a light or something to where I can hear the car idling, I don't hear it.Any ideas?.....Jason

[elwesso]

any other issues you can relate to this, can you get the noise to change at all?