I know it's forced but mines still running standard manifold and system with a sports cat, 330 bhp. So I would think the potential for further gains are there.
I would if I was still NA would work on parasitic drag, so a lightened flywheel will help there (not that much to get fitted if you find a good independent like Honda HQ in Cannock), and the oil pump balance shaft delete is good (if yours has them).
Be careful with a lightened crank pulley, make sure it is dampened or you run the risk of crank bearing/shell damage. There are some dampened and lightened ones out there, have you looked at other Honda crank pulleys for size and weight. An dampened underdirve pulley will help with gains.
An LSD will make the car handle better and more fun when off the line and islands. especially if you are changing the final drive for better acceleration. You may as well get this done when you do the flywheel as its a gearbox out and split.
You could get a manifold made with a sports cat in it or have a race manifold and a cat welded into the system as close to the manifold as possible. getting the gasses out quicker and in the right pattern is key.
Cams I would change when you are looking for power to get to around the 250+ or close to it or above.
An inlet manifold will help get the gasses in quicker, but if the exhaust manifold is restrictive then it will only be so effective on how fast you can get the gases out. I think most would say start here with a lightweight flywheel & LSD.
Personally, all the above with fitting would come to around the same or more than a second hand boosted kit
. lol (Just sayin)