Hi Steve,
It could be that the ECU will take time to readjust to the correct fuel pressure and until it does it'll keep throwing the fault codes.
I'd try disconnecting the battery for 10 mins or so to try to reset the ECU to it's default, or leave it idling for 10-15 mins.
I'm sure otehrs with more expirience will be along shortly with more help.
Good luck!
