Okay with LFX it seems the ability to impact volumetric flow modding the intake and exhaust manifold is fruitless. Cams, springs and timing chain are ****, made to hit the emissions targets and be pleasant to drive in a safe bandwidth.
However SIDI heads (combustion) are brilliant, and the stock direct injection is phenomenal, good past 500 flywheel horsepower on e85 for which the e67a computer has all the tables ready to rock.
So with a shitty cheap example LFX with stretched timing chain you do the usual per Gen IV V8 with VVT: Lift the lids port the exh a bit, shave 0.030” to raise compression to 13:1, cam(s) swap, better valve control via springs, and remap the cam events and overlap in the tune.
The effect would give SIDI a huge programmable VTEC boost with turbo-like BMEP and massive horsepower.
Using e85 the manifolds will not impede performance, huge potential naturally aspirated.