Well idve not bothered with all the brand name stuff, youd prob have spend half of what you would have, and same results.

You really want a decent downpipe as they shite as std.

2.5" bore section dont seem big enough to me either.

Next thing for you apart from all youve mentioned is a decent front mounter IMO (a std GTR one will do), can get about 300bhp from std turbo.

From then on it depends how far you wanna go, but can get 550 or so bhp and 1.5bar boost pretty safely on std internals....