Will be getting stacks for pulling next year, thought that I would be somewhat nice to the crowd... :-laf I have a single 5" system now, 4"DP into 5" by the transmission crossmember. Would keeping the 5" going into a set of 5" stacks produce any noticeable flow or performance over 4" pipe going into the 5" stacks? From the bed up would be 5" and the pipe underneath right now is 5" but a buddy wants to buy my 5". So should I sell the 5" and get 4" to the stacks or have 5" the whole way?