Sometimes referred as the ECU or ECM.  Engine (or Electrical) Control Unit or Engine (or Electrical) Control Module. 
From 1989 through 1994 Mitsubishi specified certain electrolytic capacitors made by Rubicon Electric. Mitsubishi, and Rubicon for that matter, didn't realize back then that these capacitors would go bad with time, especially at elevated temperatures. The liquid electrolyte in these capacitors begins leaking from the bottom plug as the rubber plastic material contracts. This liquid is VERY caustic and tends to mix with the humidity coating on the circuit boards. This action allows the electrolyte to spread and react with any metals encountered in its' path.

The interesting part to this story is that the bad capacitors continue to operate nearly as they should in the circuits they are in but the fluid causes other damage as an array of wide and varied problems start to occur. Problems vary from occasional rough running that can come and go over a period of a year to sudden catostrophic failure that fills the passenger compartment with the stench of burning fiberglass and blows a ten amp fuse in the panel.  Many times, an annoying clicking noise can be heard from behind the radio, dashboard, or glove box.

The location of the ECM varies depending on vehichle.  But on Eclipses and most other Mitsubishis, it is located behind the stereo.  See here for an example:  ECM Location

When these units are repaired it is of the UTMOST importance to thoroughly clean the circuit boards AND the parts in the affected areas. Many of the units repaired have been processed by different companies in the past and have lasted just long enough to go out of warranty. These companies repair the immediate problem that stopped the vehicle, stamp it and ship it. The remaining chemical on the board continues to work away on the circuitry until the unit fails again.

This chemical action continues as a computer remains in a car or on the shelf at an auto recycler to be sold by an unsuspecting counter man to an unsuspecting customer. 

Here are a few places that sell remanufacturered ECUs for Mitsubishi vehicles. Check each of the following sites for prices and availability:
http://www.foreignecurepair.com/
http://www.mitsubishiecu.com/
http://www.ecmfinders.com/
http://www.ecm-ecu-online.com/mitsubishi_part_numbers.html
http://www.avproecm.com/

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This is an example of leaky capacitors from a 1992 Mitsubishi Eclipse GS (non-turbo, Manual tranny)
Thanks Duane for the picture!
Click inside RED CIRCLE for close-up of the leak