Megasquirt

   Megasquirt is a fuel and spark computer that completely replaced you stock ECU if you want it to.  Currently, my megasquirt unit only runs my fuel system, and Motronic runs spark.  This will be changed as soon as I get time to work on my car.  It is a very cheap and very capable computer, but you must know a bit of tuning theory and have a bit of wiring, soldering and general electronic skills to be successful.