Quoted from thedefog:I'm considering doing a MOSFET job on the MPU as well.
Make sure you do it the complete correct way. Don't just 0-ohm and MOSFET, things will burn. I know.
Honestly its not necessary, I did mine just to 100% do 'everything'.
If you still feel the need... just replace the 27-ohm resistors with 5w SQT ones more spaced from the board.
If you still feel the need for the extra mile for the mod be sure to do the "Voltage Divider" implementation
http://www.pinwiki.com/wiki/index.php?title=Data_East/Sega#Using_MOSFETs_in_the_Lamp_Matrix_Circuitry