Too much of a good thing? Has any one one tried or know if it's possible to use an aftermarket upper like a Kinetix Racing V+ intake along with a spacer? I'm thinking it would work great with a turbo, but what about NA?

 

Clearance issues with the strut tower brace is usually why. However Tony at MD had some dyno results that the OEM spacer thickness being larger started to reduce midrange torque pretty significantly, depends on WHERE you want to make power and 5/16 was the happy medium for daily driven vehicles.

The greatest strength of this chassis is the handling, you wouldn't want to sacrifice that for a possible 2-3 hp.

Forced induction is a whole different scenario though since your intake restrictions aren't normally a problem at that point even with the stock no-mods plenum. Getting air OUT OF the engine is usually the most restrictive factor for FI.

 

Usually more plenum volume helps max power (smoother flow through the throttle and such increases flow at high speed when they become restrictions), but it takes up space and transient response is worse without ITBs or with forced induction since the bigger plenum takes more air to pressurize.