Ground your radio. And by "ground" I mean an RF ground which you get
by mounting the bracket directly to the metal and/or using a -=SHORT=-
ground wire. You can't fudge on this ground.

I'm using an L bracket screwed straight into my fender, it sticks out
from under the hood. Pretty sure it's grounded. I've tried a grounding
strap anyways on the antenna, and no difference, unless I ground the
whip of the antenna, then my antenna doesn't work

Dude, that's some terrible gas mileage. Maybe your car just needs a
tuneup..... hey, I thought you said it was a truck?

Yeah, well, I live on a VERY steep hill, my house in on stilts, our
driveway is fill dirt and flat enough to park a car on, but anywhere
beyond the fill dirt is so steep my truck will roll over. Unfortunately
my 'flat spot of parking goodness' isn't bigger than 50'x30 with the
powerline for the house going lengwith along it.

I guess I might want to look into a combo base/mobile rig, so I can run
some coax down the hill to an antenna and get away from the powerlines
or park in front of my neighbors house to talk. (People give you
strange looks if you park in their neighborhood with your dashboard
tore out, frantically trying to get a QSO).. One word.. TERRORISM.