In addition to the weird electrical problems and strange Dashboard readouts... these other issues apply if your 1995 5.7L is using the "Old OBD 1" Engine Management System. And as for the Engine Idle problems, more than likely... you have already addressed most of what follows:
On A 22 year old truck… a whole range of things can cluster to cause problems... and so your Vacuum Hoses are going to be a little sketchy at their connection points and should be investigated when the engine is idling for being easily pulled off and obvious signs of age and cracking and a response to being manipulated that might pinpoint which . Next, your Throttle Body will probably have a buildup of Carbon and Dirt residue in the venturi chamber and around the Butterfly plate and might have tendency to “stick” open when stopped at a Red Light and allow air to bypass its normally closed position and cause the engine to idle higher… or “stick” closed and cause a jumpy start when you have to step harder on the gas pedal… making the truck lurch once the plate snaps free.
Again… when stopped at a Red Light and experiencing any “surging”… the (IAC) Inlet Air Control Valve mounted on the Throttle Body could also be clogged up with Carbon and be plugged up in the small air passage it controls to meter air into the engine when the gas pedal is not being pressed to maintain a proper amount of air by-passing the Throttle Body Butterfly Plate and keep the engine running and not allow it to stall. This is a non-serviceable component and an OEM replacement part is in order.
If The Throttle Body is equipped with a (TPS) Throttle Position Sensor… it might also need replacing, right along with the Throttle Body Gasket could also be sketchy enough to allow the unmanaged air to vacuum in below the controls mentioned above… and consequently… removing, cleaning and re-installing a thoroughly cleaned Throttle Body using only proper solvents that won’t damage any sensors. Disconnecting the Battery Negative (-) Cable just before a 30 minute servicing and cleaning of the Throttle Body will allow the vehicle to adjust to any replaced sensors. Using OEM TPS replacement units is recommended here… and New Gaskets as well.
One last problem that is often not obvious, but has been observed over time are Leaking Upper and Lower Intake Manifold Gaskets that allow Coolant Passages to weep Coolant around the perimeter of the engine. Unless its obviously present, this should be the last issue to investigate as these problems would also allow unregulated air to enter the Fuel-Air stream and cause the engine to idle quite high as more fuel is being added to compensate for the excess O2… especially when the engine is Cold… and this issue will not throw engine codes.
Here is a link to CRC’s site on the proper cleaner and techniques to follow:
http://www.crcindustries.com/auto/?s=05078