Okay I have had this problem ever since I had Best Buy install my remote start and keyless alarm system. Ever since then I have heard a whinning or hissing noise coming from my footwell on the drivers side, seems to be coming right from under my pedels. It isn't really noticeable unless the radio is low and I'm trying to talk to someone. It wasn't there b4 the install(a long time back now) but I really just got over it and accpeted it, but last night I heard it while I was trying to talk to my girlfriend and then only thing I could think of was how annoyed I was by that whistling sound my truck was making, you only hear it when your accelerating, any tap on the pedle brings the sound. ANY idea of what it might be and how I could fix it?

 

That definetaly sounds like a grounding issue, and it speeds up as you say when you accelerate.

Do you have an amp wire down by there that goes up to your battery?
Could be they have one of their wires from the install right next to it.

I'd take it back and tell them to diagnose it and get rid of it.
See if that unit for the alarm is down by where the noise is too.
Might be something in its black box making the noise.

 

Isn't the hole in the firewall in that area? Maybe there is a hole allowing sound to come in through there. If its not a stereo related problem... and its only comming from the driver side... i could be completely wrong, but I believe thats where mine was...

 

Definitely sounds like a grounding issue. Like Corey said, a bad amp ground will DEFINITELY cause that to happen. They could have even attached one of the alarm grounds to the ground that your amp uses, making the amp's ground not as grounded anymore.

 

Also on what Austin mentioned, Jim had an amp and speakers added to his '89 truck early spring, and the shop did not seal up the firewall.

Turns out it was letting in a lot of engine bay noise where the amp wire ran out from.
Corey