Actually, the 24 to 28 pin change happened sometime in 87. I know because mine is 28 pin when it generally speaking should be 24 pin. It is easier to run a 24 pin in a 28 pin setup than the other way around, though. Just clip the jumper and install the chip with pin 1 on the chip backspaced 2 pins from pin 1 on the socket.
86 to 88 Conversion ML3.1
Brody, any chance you will offer a tuning specifically for cars with no cat, or tuned for higher octane fuel?