If you're autocrossing, be careful of which modifications you make as they can push you into SSM or CAM-S - running against Vipers and C7s.
Have the head soda blasted, checked for flatness and decked if necessary. The machine shop should also do a valve job, replacing any springs, etc. where necessary. My local guys did the whole thing on my 2.4 head for $250 and turned it around in 24 hours, though YMMV.
Port and polish are obviously good for airflow, but I haven't seen much - really, any - mention of what's been done in that area on these engines. For your application, I suspect that would be overkill. (Though, if you can get it done cheaply, why not?) Talk do Dave at DDM Works - he can give you some pointers.
While the engine is out, I'd consider an aluminum flywheel and possibly upgraded clutch. I got mine from Performance Autowerks. DDM also has great units. The flywheel made a huge difference on my 2.4 (turbo). It revs significantly faster than my 07 GXP.
Anything you do that reduces the mass of a rotating assembly - pistons, rods, crank, pulleys, flywheel, driveshaft, axles, wheels - will have a significant performance impact. Compare the weight of the new components you're getting against the stock units. Adding mass to the bottom end is a huge performance killer.
Blue-ish 2006 2.4, Werks stage 1 turbo, Borla cat-back, DDM braces, Spec aluminum flywheel, Spec stage 2 clutch, Werks aluminum radiator, some gauges, RKSport hood, Morimoto FX-Rs, GReddy Profec, Norm's fenders
'07 GXP, RPM Stage 2, Solocatless downpipe, TCE Wilwood 6 piston front brakes, 4-piston rears , Stainless brake lines, slotted/drilled rotors, BC Racing BR coilovers, Performance Autowerks intercooler, DDMWorks CAI, charge pipes and braces
Last edited by raygun; 07-10-2018 at 10:18 AM.