Murphy said while van Gisbergen's Tekno Racing team have an alliance with Triple Eight Engineering, there is always a disconnect of sorts.
"It is hard to be better when you are sharing the information and you do not have the benefit from the development that two cars have on a daily basis."
Next year Coulthard moves to Team Penske and van Gisbergen jumps to their technical partner at Triple Eight alongside Craig Lowndes and Jamie Whincup.
Murphy is adamant Penske Racing will become a force in V8 Supercars.
The organisation, under global motor industry giant Roger Penske, is already successful in motorsport in the US, and signalled their intentions with the addition of a second car which Coulthard will pilot.
"The team is going in one direction," Murphy said.
"There will be no excuses and they will do what is needed to win. Both Shane and Fabian have their best possible opportunity to reach the top in the sport."
Murphy hopes one of the Kiwis will claim the spoils at Pukekohe next weekend.
"Shane comes in winning form and Scott McLaughlin was very fast in the Volvo at the Gold Coast. Fabian has always done well at Pukekohe and, of course, their team has added incentive when it comes to wanting to win the Jason Richards memorial Trophy.
"It is also Andre Heimgartner's best chance to shine with Super Black Racing on a track he knows well."
The ITM 500 Auckland begins with a driver parade and fan day at Aotea Square on Thursday, practice on Friday, qualifying and two sprint races on Saturday, a fan walk before qualifying and the final 200km race on Sunday.