Set Appliance State:

Gas Off
Isolate Mains Power to appliance as per TOPs P4
Turn Hot Water Tap On
APS test kit still connected as in previous test
Depress syringe so performance tester reads 0mb
Refit wires to APS but leave tube to fan disconnected
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Reset appliance as necessary.
Allow the boiler to begin it's ignition sequence.
Approximately 2 seconds after the fan starts to run withdraw the plunger on the syringe until the pressure indicated on the FGA is equal to that at which continuity / zero resistance was measured in the previous test.
Can sparking now be observed between the ignition electrodes?