Derf00

^^^ and is that stuff usually found at your regular run of the mill corner auto parts store, or is it special order?

I should clarify, the stuff they sell in auto parts stores is a sham.

Stangbass

The NOS octane booster they sell at Wal-mart and the big box auto parts stores works pretty well. It has the same main active ingredient as Torco(MMT). It's kind of hard on the plugs though.

JayGee

Thanks for all the input guys. I've been driving the past couple days with the same conditions (windows down and music on) and it's not noticeable at all. I think it's just been there this whole time and I just recently noticed it. I remember hearing the same kind of noise in my old f150 before I got rid of it (wasn't interested in cars or trucks at the time so I thought nothing of it). It pulls just at hard as before so I'm not going to worry about it for now.