I have to go to a car intake due to hood clearance problems and for the past week have been researching this topic ad nauseum. The end result is as you were told, LS1 manifold ports flow worse up to .500 lift. The LS6 will flow better across the lift range and rpm range. However, you will pay $325 and up for LS6 vs $50 shipped for LS1. The project I'm building doesn't reqire big HP numbers so I cheaped out with an LS1.
Keep what you have unless you plan on spinning 6k rpm or more. If you are the LS6 is more manifold for the buck than a FAST.IMHO
Bob

 

I would not go with the LS1 manifold personally.

 

What about a TBSS manifold? On the 07' and up trucks now as well, correct? A better option than any mentioned yet IMO. Power characteristics needed for a truck, in a 90mm TB setup (maybe 87mm, not sure). Probably would net very comparable gains to the ls6 in hp and torque.

 

There was a good thread about the TBSS manifold recently, it showed some impressive gains throughout the RPM band.

 

ha ok so i hear! thanks for the clear up

 

i havent seen much about gains from the tbss, but i see them for sale quite a bit