does open headers increase hp/trq or decrese it?

[driftfreek]

i was thinkin of racing with open headers in da track, but then i thought... i might lose some hp/trq?wat do u guys think?

[neverlift]

my 00 jimmy with 4.3 liter vortec on open headers fell flat on its face,sounded great,and then screamed on the top end. I was shocked to find a beefy v6 loose so much trq, but it did gain hp up top. It would not break traction,but with stock setup it would easily. Not a I4 but still lost and gained. Give and take I geuss.