Mk2 FL VRS cutting out after changing fuel pump

I was getting an error code relating to fuel pressure regulator and power loss on my vrs estate. I was advised by a trusted person that the pump would be on the way out.

Changed pump and the headaches started. Fuel gauge is no longer working and car cuts out intermittently whilst driving. 

The car starts first time and does not cut out on idle. From what I've read it must be a relay or some sort of other electrical issue. I'm pulling my hair out as I've changed relays in engine bay and changed fuel pump control module and still no joy.

Any help would be very much appreciated. I love the car and just want the bloody thing running again.