Anybody know about the BMW 318i '85 electronics?

I'm too lazy/cheap to get a service manual.  Anybody know about
the onboard diagnostics in the '85 3 series? (if there are any)
I've heard that the custom upgrade/hack I was contemplating (using a carputer
(computer in one's car) to upgrade/downgrade electronics "on the fly")
was possible on pre OBD-II cars.  By on the fly, I mean as a simple circumvention
of the "junker's first law of performance" (the more performance, the shorter
engine life) or so I call it.  My idea was a special governor chip with an
external BUS that I could hook via USB to the carputer (which would have the program
to do so installed)

I guess my rant's been confusing, so my question is this:

   Is there a reprogrammable chip or hackable bus in the PCM or
   ignition control module of the car?