Whether you're running a standard distributor type ignition system, or a programmable aftermarket ECU it is essential that the ignition timing is correct for the engine, not only will this ensure the best power is achieved it will also help ensure the engines reliability.
To much ignition advance will quickly destroy pistons on a forced induction motor this cannot be stressed enough !
A slightly advanced ignition on a basic naturally aspirated motor will rarely cause a problem, but on a Turbo engine it can easily cause detonation & lead to complete piston damage & an expensive rebuild.

42628 is the part number for the mini turbo and the MG Metro Turbo dizzy.

Standard ignition timing is 7 degrees BTDC at 1,500 rpm with the vac advance pipe disconnected.