Ok I have the headlight thing figured out. Thanks.
As far as the engine vibration goes, it's very hard to describe it. It's one of those things that you really have to feel to understand it. I'll do the best that I can with my description.
As I'm driving and near 70mph, the car starts to develop a steady rumbling noise that sounds like it's coming from the engine. The car vibrates as well, specifically from the engine and the floor area near the pedals. It's almost as if the car is having to work harder than it normally should to suck gas through the line because the line has developed a build-up on the inside walls decreasing the amount of gas it can pull through.
The car doesn't hesitate or jerk though, and the loss of power is hardly noticable. I've had a new fuel filter installed and the fuel injectors cleaned, to no avail, which leads me to believe it's not fuel related.
Also, and I don't know if it's related or not, the car has a hesitation at low RPMs. For instance, if I'm sitting in line a drive-thru and lightly press the gas to pull up, the car jerks and speeds up and slows down while I'm holding the gas at one point. I've done a test and at around 1000rpm, when I hold the gas steady, the car lurches forward and slows down, and the RPMs go up and down between 500-1500rpm.
Again I don't know if that's related, but thought I'd mention it.