I had a full service on my fresh import when it landed a few months ago. Belts, water pump, plugs, box serviced, diffs serviced and most importantly, re-mapped for the fuel I was going to use (Shell 99 Ron). Whatever you do, have it mapped for your local fuel. I also had a full Dinitrol rust treatment done on it. I won't use it in bad weather, just had it done for peace of mind.
I wouldn't bother with the cats/downpipes etc. These are not far off the limit performance wise on the stock motor (280bhp for the manual). 300bhp about the limit on stock rods on the JDM motor. Everyone I know with one keeps them to about 1.2bar. Any more, they all end up throwing a rod.