Cheers for the help, i hadnt had any replies before i fitted it so just went from a live feed off the ignition that cut out when cranking, it wasnt the way i really wanted but it is actually working ok. the gauge seems to zero ok and when driving hard registers a max boost of a shade over 1 bar which is what im told it should max out at so im assuming the gauge is ok.
thanks anyway guys if i decide that i do need to change the connection i will follow your advice and go with the relay.