i just installed a used ported 90 MM FAST INTAKE. i replaced an LS2 OEM GM intake.engine is a 2002 LS6 CRATE motor .550 lift cam, SLP HEADERS, GMMG exhaust. i have had the LS6 INTAKE also that came with the engine. LS6 was a great all around intake, bottom end, top end, and gas. LS2 was great on top end beyond 3000 rpm and great on gas.slow on rpm's.
the FAST INTAKE is just awesome from a bottom end standpoint. i am pushing a 342 OEM rear end and the rpm's just scream. i have noticed a slight increase in gas consumption. uses the same FUEL RAILS.
i have not attempted to run times on any of these, but my conclusion is save your money on swapping LS6's, LS2's, etc. for a few more dollars you can go to the front of the class unless you like looking at my rear-end.