Sounds like its coming from the fuel pump? I have plans to change the fuel filter this weekend and the rear drivetrain fluid. I really think its coming from the fuel pump though. I'm wondering if my fuel filter's clogged and forcing the fuel pump to work too hard? Anyone had a similar issue? I pulled the plate off that's located near the spare tire and I'm almost positive the noise is coming from the pump.

 

I'd go with the filter replacement first to see if that does the trick. Worst thing that can happen is you have to change the pump. While you're there it's probably worth taking down the pump and draining it, lightly blowing out the fuel.

Odds are thiswon't cure the problem, but it's worth a try before paying for a new pump. Be carefull with the clamps and fittings.

TBM