On the back of the standard FIA approved master, there are
2 auxiliary switches. One breaks connection when switch is
closed and the other makes and visa versa when switch is opened
i.e. off and take key out.
Standard they are wired so that switching off disconnects supply
to the ECU. The other aux switch connects the protection resistor
to the alternator output, to prevent damage as engine spins down
if the master switch is turned off with the engine running.
On my installation, I have bridged the switch which supplies the
ECU so that it always has supply regardless. You could just join
the wires together, but having a bridge with blade connectors means
you can quickly remove it when in competition; as it is a legal
requirement that if the master is turned off, the battery is totally disconnected from the cars electrics.
If power is disconnected from the ECU, it will loose it's map and will
have to learn all over again. That is why your car runs like a dog every
time you turn your master off. This only applies to the O.E.M Rover ECU's.
After market ECU's in almost all cases do not work like the MEM's for
instance. They will have a lookup table in ROM, which is non volatile.
For road use bridge the switch. Also if the Rover ECU is kept supplied
as I have stated, it will flatten the battery in a few days as the
immobiliser sucks quite a few milliamps.