for porting.... raise exhaust 1mm , widen exhaust 1.5mm both sides, match intake and exhaust ports to whatever manifold and pipe you're using. you can obviously go crazier but this will be a good starting point. the performance will be noticable. CHAMFER
if you're feeling it you can shave 1.00-1.50mm off the intake side piston skirt for a little more boosties. chamfer that too.
also I would recommend ditching the stock pipe... have you considered what kind of aftermarket one you were gonna possibly upgrade to?