I think 'negate' is a very poor word here. The more appropriate word IMO is 'override'. The turbos will override any ram effect with their greater ability to create increased pressure.

Whether the turbos would have any effect on the intake pulsing when the intake tract is under vacuum would be a very interesting question however. It would be in the same list of questions as 'were the long rams tuned only at WOT or at partial load'