86 GT Engine and Fuel Questions

[Comatose]

I read in another post about a fuel pump whine. My 86 has a very prominent whine or hum coming from the rear of the car while it's parked.....is this normal?

Also, the idle is inconsistent. It will sometimes idle at 1000 rpm, and sometimes idle at approx 575-600 rpm. When it idles at the 600 rpm, it doesn't vary at all, when it idles in the 900-1000rpm area, it surges mildly. The throttle response seems to be better when it idles at 1000rpm, in the 600rpm range there is some hesitation.

When I come from a dead stop and stomp it, the throttle response is good, but at the next stop light, it idles about 1300rpm. Gas mileage has gone down 2-3mpg as well.

Please Help.

Mods are: Hypertech chip.

Thanks for the help.