2005 Chevy Impala funny smell

For about a 2 weeks now I have smelled something like a electrical burning smell and can't find a thing wrong. No fuses out, all circuits seem working fine and no hot relays or wires? It comes and goes and seems strongest comming from the fuse box on pass side dash? Nothing under the hood or anywhere else?

updated post 1/28/09
Never smells outside the car, and is not any different with or without the heater on. Seems to be comming from the pass side fuse box located in the dash thats where it is the strongest. No hot wires or relays can be detected and no fuses blown?