I personally second the spacer ordeal. never have I seen a spacer before the manifold be beneficial to any amountable gains. under the intake manifold, yes, as the velocity increases... but between manifold and TB, not really anything as most spacers aren't wide enough. at best its a good area to add a vacuum port or some sort of injection nozzle for meth, water, nitrous, etc...
the spiralmax, has been shown numerous times to decrease HP, dyno tested MANY times.
especially and mainly mid range and upper rpm, as its a restriction in the tube. the tube is there to flow air. if you start adding all sorts of gimmicks in em to make turbulence in the air, you reduce performance.
basic bottom line, on any performance car will you see anything in the air tract. I mean nascar and other BOP balance of performance sanctions run plates that restrict air to take away power...which is essentially what those do.
if a tube is to flow 300cfm at WOT, and you throw some contraption to swirl air in there, the mass of the turbonator/spiralmax, then reduces the flow to lets say 265-275 cfm. that's detuning an engine in its simplest form. higher velocity allows for more air to flow, anything in the way slows it down and works against getting air flow. not to mention the turbulence those were designed to create were from port injected engines... the LFX and now LGX are direct injection, meaning no air and fuel mix until in the combustion chamber... so turbulence in the air intake tract is a waste since theres no pre-mixing. velocity and air speed means more flow. hence the reason with ported manifold, the idea is to remove the venturi tabs that stick out, as its a restriction. ported manifolds work, and the whole idea is to remove anything in the way of air flow...not add things to the air ways...
outside of those two things, all else seems solid.