WTF is this sound, pinging?!

[MineralGray02K]

Well when i shift from 1st to 2nd, then let off the clutch and push the gas down, i hear this noise that is coming from either the engine, or somewhere around it...I noticed it the day i drove my car off the lot with only 50 miles on it, know it has 3600. it's a 2002 mustang GT, in 5 speed...the noise almost sounds like a mix of clicking, and the noise when your about to stall out, and u clutch it, you hear something raddle or shake or something. I really hope it's not ping...It doesn't just happend when shifting, it also happens if I'm driving in a gear, then hit the gas, it will make the noise for a split second, then not stop. I don't feel a power loss, or maybe i'm used to it, I don't know. I really hope it's not ping. All I have is the K & N intake w/o silencer, and flowmasters. Is it the intake sucking in for that brief moment? AHH!!! thanks.