Cadillac Repair: engine loses power when driven for extended peroids, radiator fan, peroids

Question
What could cause this problem. I think maybe its electrical but I dont know for sure.I have a 91 sedan deville front wheel drive, 4.9L fuel injected v8. It loses power when it gets hot and wont pull hills. When its cold outside it runs fairly well on short trips like within 10 or 15 miles, nothing extended though it will usually start losing power and eventually stop altogether. I will let it cool for about five minutes and then I putt home. expressway driving is pretty much out of the question. It ran great when I lived in Ohio but since I moved to Colorado its just not the same car. Also the fuel economy gauge cycles through all the settings continuously and wont stop on any one indicator for more than a few seconds. gals/mpg/miles to go/fuel quantity ect.
Any help you could give me would greatly appreciated.

Answer
Hi Jeff, It would be nice to know what fuel pressure was when this is happening. Maybe you have a restricted fuel filter. Also there is a gas tank vent up by the LH radiator fan that maybe plugged and gas is haveing a hard time getting out of the tank. Try driveing with the gas cap off and see if that makes a differance. The other thing that comes to mind is a bad MAP sensor. It is supposed to tell the computor that the altitude has changed and you don't need as much fuel. As for the display there might be a button stuck or it is just defective and needs to be replaced. Bill