Ok update,

Soldered in some wires tonight and got a reading of 12.7v. Better than it was but still down on what everyone has been saying.

Took the car for a blast and the missfire is still there

Once my new pump & filter arrives i will run a fresh wire from the Batt and fit a relay.

oh well the hunt goes on, loom multi plugs next and then we are looking at changing out the chip.