First my question is what is a my 03 5.3L intake manifold made of? It looks like some composite, plastic and fiberglass material.

My next question is has anyone tried installing different manifolds? I just noticed that weiand
and other companies manufacture them. Any hp improvements found?

Check out this awesome LS1 compatible intake manifold. Supposedly it can yield hp gains of 12hp.

http://www.weiand.com/HiOctn/ProdLin.../300-111P.html

<small>[ April 04, 2003, 05:01 PM: Message edited by: MarineBlue03GMC ]</small>

 

all of the generation 3 intakes will fit, but with some modification. there isnt really any need for changing them because the truck intake flows just as good as the f-body. the truck intake makes more torque anyways. this really isnt work doing in my opinion.

 

The truck intake should give you more mid range torque, but will not give you the same HP as the LS6 intake. For max upper rpm power, the LS6 would be the best choice. The aluminum one is very similar, but it can also conduct heat where the stock composite intake will not.

Physically changing the intakes will fit, but it will take some major reworking of the accessories to clear the lowered throttle body.