1991 Eagle Summit

I have a 1991 Eagle Summit with a 1.5 engine with 141000 miles. I have replaced the computer, the distrubutor, the plugs and wires, the temperature sensor in the radiator, and the fuel filter. It has an intermittent problem of just quitting. It won't restart and the fuel relay clicks. I bought 2 more relays at a recycling yard, changing them does'nt make any difference. I put 2 circuit testers in the 2 hot leads to the relay, they both stay hot during the problem. Let the car set a couple hours and it will start and run till it decides to quit again. At one time it seemed to be caused by medium to high rpms. The last time I drove it, rpm range did'nt seem to be a problem, in fact it quit at avery l;ow engine speed.
I have put only 3000 miles on this car in 2 years because we cannot count on getting there and back.
Please help, I can't sell it or anything like this.