Mitsubishi Repair: speed/overheating, wiring harnesses, fuel pumps

Question
HI, I HAVE A 1992 1.8L ECLIPSE W/ALMOST 200K MILES ON IT,THE PROBLEM THAT IM HAVING IS WHEN IM DRIVING 70MPH MY ENGINES SOUND LIKE ITS HAVING A HARD TIME AND OVERHEATS DURING UPHILL DRIVING W/OUT AC ON,I HAD THE TIMING CHECK AND IT WAS FINE,HAD NEW THERMOSTAT INSTALLED NEW ALTERNATOR.AND WHEN I ALMOST GET TO A FULL STOP THE CAR WOULD ALMOST DIE OUT AND SOMETIMES ITS DIES OUT.I WAS TOLD THAT MY ENGINES IS WORN OUT AND HAS TOO MUCH MILES ON IT,COULD THIS BE THE PROBLEM?IF THIS IS THE CASE IM THINKING OS SWAPPING A 2.0 NT ENGINE ON WOULD I HAVE PROBLEM INSTALLING THIS?THANKS

Answer
Ed,
Even with 200K miles on your car, your engine is not worn out unless you haven't been keeping up on regular maintenace items (all listed in your owners manual).  If you did not have your entire coolant flushed when you installed a new thermostat, you may want to consider trying that.  

Also, replace your air filter and fuel filter if you have not done so for more than 2 years.  Have your Idle Air Control motor and your fuel pump inspected as well.  If your fuel pump is weak and not providing enough fuel, your engine will need to work harder and that too can cause heat build-up.  Most fuel pumps don't last 200k miles, so if you're still using the original fuel pump, you may need a new one.

Swapping in a 2.0L engine into a 1.8L Eclipse is not recommened.  It would be a lot more expensive to swap in the engine, computer, wiring harnesses and transmission (along with all motor mounts, hoses, etc.) than it would be to simply buy 2.0L NT Eclipse.  
Good luck!