I have often said that every engine has a “restrictor plate” and that would be the intake manifold. Over many years we have tested many manifolds on and off the flow bench just to see how restrictive they really are. Some factory LSx manifolds impede total flow through the cylinder heads as much as 60+ cfm! Much improvement can be had from porting not only the factory intake manifolds but aftermarket ones as well.
Whether it be removing sharp edges, re-profiling bell mouth entries, re-shaping throttle body bores or port matching the manifold to the new CNC ported heads, there are gains to be had! While some of the peak gains can be fairly minimal (8-12 rwhp peak), the area under the curve and acceleration rate of the car are greatly improved upon. Results will vary, as some of the factory LSx manifolds are worse than others.
(Factory Throttle Body porting also available)