Who told you that??? I will repeat this is a great myth fabricated by people who do not understand exhaust science.
When you have a X, H or any other type of crossover pipe on a dual exhaust you still have dual exhaust.
The real need for a X or H on a V6 is up for debate. The need for X, H or Crossover tubes is well documented on V8's.
So no matter what Mechanic, Teacher, Priest, Pastor, Relative, Friend or Friend of a Friend said
THEY ARE WRONG!!!!: