If you blow an engine it'll be your own...here's
how:

Start with your 747xxxx.bin and 747.ecu file
  in the current directory and "promedit" in
  your DOS path.
Run "promedit 747xxxx.bin 747xxxx.1"
At the "Enter Table Data File name" prompt enter
  "747" (or the name of your .ecu file less extension).
Press "F2" for a list of tables.
Enter a number corresponding to a table (ie "1" for
  Spark Advance")
Press "Shift F2" to jump to the next table or "Cntrl F2"
  to jump to the previous table.
Press "x" to toggle displaying the tables betweem "Raw"
  hex data and "Converted" data.
Select the table value you'd like to change. Press "+"
  or "-" to increase or decrease the value.
Press "?" for help on these and other commands.
Press "q" to quit.

Your new bin file is called "747xxxx.1". Generate a new 
checksum, burn the EPROM, burn a piston, burn another quick 
grand or two and start the process all over.  :)