From the head you cannot see any big HP difference in forced induction.
You can help the exhaust system if you polish the exhaust side of the head.
If you plan to move on to the big HP levels (more than 500hp) you can port the intake side too.
the big difference that you can notice easy, should be from the cams.
But the cams must be chosen depends from the turbo manifold,engine,turbocharger etc.
you cannot use an agressive N/A cam on a B18 engine with log or cast manifold and a turbo with .63 A/R on the exhaust side. the back pressure on this combo is an HP eater.
In general,
B16 cams or GSR better should be use and works perfect with log/cast and sometimes with minirams, with turbochargers with .63A/R and max rev at 8.700, 2.5"-3" dp and exhaust etc.
ITR/CTR or bigger cams works well on ramhorn/top mount manifolds, bigger turbos .82A/R +, 9.000rpm+,3"-4" dp and axhaust etc