This thread got way off topic fast...

I may be able to clarify some things here in a bang for buck sense.

To the O.P.

start by forgetting a full intake.. Just buy a drop in K&N panel filter and remove your intake resonator.
Changing the material of the intake tube yields no gains other than cosmetic. Cosmetic = Cop attn.

Exhaust wise, find an 06 cat. Bolt up a PLM header and leave the rest. PLM have the most durability second only to Toda and there results are respectable.

Suspension, forget lowered springs. They a waste of money. Buy an entry level coilover such as Tanabe Sustec Pro or BuddyClub.
BC coils are a lot harder than Tanabe, so choose based on how the roads you drive on are.

Rear camber.. Try and delete as much of it as possible. Avoid Skunk2 (Junk2). Get Hardrace, Good pricing.
RSB. I had, then returned to oem. Front Bracing is also not really an improvement, if anything a rear boot brace only.

Tires, buy good ones.

Those basic bolt on 1hr jobs will make your car a heap more entertaining to drive. If later on more power wanted, then drop in either an 06 CL9 intake cam or TSX (if you can find) intake cam. No EMS upgrade req for that.

If EMS upgrade happens Its a good idea to fit a CU2 exhaust cam gear to your stock exhaust cam and a K20A vtc intake cam gear. Also try and use the K20A upper timing chain guide. It has a much larger surface are over the chain up there than the K24 Euro or TSX item. Leave the chain tensioner alone too.

Lightweight pulleys are ok.. Just not under drive ones.

Flywheel makes a huge difference, leave the shift bushings alone. Unless there worn the only replace with oem. Not solid because you will break the cables very quickly.

Intake manifold also leave alone, the costs to change and the highly debatable results aren't worth it at all. Just do the usual T.B coolant bypass trick and maybe bolt on the 06 throttle body + thermal gasket. P2R spacers also do nothing.

All in all very easy and cheap things to do.

Been thru it more than anyone knows lol.