An "H" pipe - or even better - an "X" pipe will add about 5 HP to your combination if you rev it to about 4000 RPM. Less at lower speeds. It is up to you to determine if the expense is worth this kind of gain.
To me it is, assuming it is neatly packageable.
My opinion is based on thirty-some years of engine dynamometer testing observations in the Engine Performance Development Group at Ford Motor Company Research and Development Center, Dearborn, Michigan.
Your results may vary.
But I wouldn't bet that way.
