[size="6"]Hi, im looking to get more horsepower out of my st205.

Mods:
Straight pipe with Megan Racing muffler
manual boost controller
hks intake
blitz bov
walbro 255 fuel pump
arp head bolts and studs.

What are other things I can do to get more hp?

Hi,

just the boost controller and the exhaust gaves you power, everything other is useless on the ST205 if you use the stock engine and ECU

you can go for a TTE TMIC, which kicks the boost up by 0,1bar, a exhaust system with 200CPI cat (or less), gives you another 0,1bar, which means you are around 1,1bar boost
which is the boarderline until it becomes danger for the engine, here around is also the fuel cut point

i was driving my one without any boost controller at this stage and had often fuel cuts in spring and fall, one further tip is go for a high amount of water in the IC system, i used 1/3 anti freeze and 2/3 water,
the heat cunductivity and specific heat of anti freeze is terrible against water

no need for a fuel pump with oem turbo, the same on the head studs, i would never use a open cone filter in the engine bay, the blitz bov is nice if you want sound but there is no further advantage against the oem one

hope it helps

greetz