Just got new ECU to replace my playing up one (hopefully)
2 questions.

1. Do i just disconect the battery and unplug the old ecu and plug in the new ECU and reconect the battery? or is there a "correct" way of doing it?

2. On the bottom of the ecu is a little plastic cover. (broken on mine) when removed it reveals a part of the pcb inside that looks set up for a female plug to go onto. anyone know what this is for?????

I haven't done it personally but it sounds the right way to do it. The port on the bottom is called the J3 port. It is where an aftermarket chip gets plugged into eg capa eliminator chip, powerchip etc

^ bingo

The blue part is a J3 chip.

Thanx guys.
Data_Mine, whats a j3 chip? and you still burnin chips for ef's??????? Just askin you cos you seem to know what your on about with the electronic side of things.

A J3 chip simply (electronically) replaces the code stored on the ECUs memory, since they are flashable like those on BA's and newer.

From there the code is tweaked to make the changes you require. The hard part is knowing how to make sense of all the code. Which is program code, which is fuel maps, spark maps, etc.

I only ever managed to be able to change the rev and speed limiters on my EL.