oxrabidus

Hey guys its been a wbile since i posted on here. Had to sell my iroc unfortunately. Ill eventually get another one.
But for now i have a chevy 1500 with a pitiful v6. Im building a near stock
350 tbi. Gonna port the heads and intake manifold a bit and do he ultimate tbi mods.
Im really interested in the xfi252 cam. It seems very. Omputer friendly and doesnt require headers. Although i may or may not get headers i dont know yet.
But i used comp cams camquest software and it told me that a stock headed and stock tbi intake with a 500cfm tb would make 279hp@4000rpm and 447ft/lbs@2000. That was with long tubes and no cats with mufflers. With stock manifolds and no cats it went down to around 240hp and a few less torque.
My question is if the difference between long tubes and headers is realistically so little, should i just get manifolds? Its gonna be a daily driver truck and i just want torque mainly so maybe manifolds will help the torque down low as oposed to headers?
Also how acurate do you think thise numbers are? They sound pretty nice although too good to be true.
Thanks
Miguel