Fuel pump variants 318i

[Ballo]

Just finishing my 85 318i automatic restoration and the in line high pressure fuel pump packed up ! Simple fix ? Fitted new pump but now revs surge in Idle between 750 to 1250, won’t rev higher, eventually cuts out.
Apparently some pre facelift models have a low pressure in tank transfer pump to the external high pressure pump and some don,t, my question is are both h.p. Pumps the same or is one different because it has to draw fuel from the tank ? Any ideas on if this my problem appreciated