C280 W202 with megasquirt
 

Hi All
I've got a '95 C280(W202.028 with the M104.941 motor) 4sp auto i'm planning to eventually supercharge but need to first take control of the fuel and spark management. Working on a tight budget and opted for the megasquirt approach.
Taking this one step at a time and only want to get the car running before moving on to forced induction. Dont ask why, i just want to since i'm a merc and performance fan and can't afford a car with the kind of horses i'm looking for.
This is the model with the biodegradable engine harness, i've just manually fixed one wire at a time.
i know this is not a new subject but have already done a lot of reading on this, other merc and the megasquirt forums but can't find specific info on how to wire-up the megasquirt 3.
Can anyone who's done this before provide more info on any of the following questions:
- Does the megasquirt 3 completely replace the standard ecu/ecm or am i looking at a hybrid(piggy back) install because some electronics like the speedo and rev-counter are still driven off the std ecu/ecm?
- The transmission is also connected to the std engine harness. Can the megasquirt 3 control this or is the std ecu/ecm also still needed for these?

some people leave original injection alone,and run a additional injector before throttle body,and use a timesaver to fire it when needed.