Hi guys, first post as I知 new to the Subaru world. Just purchased a 2010 sti type uk hatchback and I知 absolutely loving it!

Car has had a lot of work done by the previous owner including:

Ej257 long engine forged rebuild
block converted to closed deck and 14mm headstuds
Ej257 block bored and honed and block faces skimmed
mahle 2618 forged pistons
acl race series main and big end bearings
Williams H beam rods arp2000 bolts
New Subaru 11mm oil pump
New crank seals
14mm headstud conversion
RCM MLS headgaskets
Injen CAI
forge dump valve
Engine build done by Andrew Williams at Williams competition engines

Couple questions for you guys, I知 led to believe that this engine is good for 500hp, does that sound right to you?

If so I知 hoping to make around 400hp or there abouts with it, what would I need to do in order to achieve that sort of power? I currently have a dyno printout of 340hp but I知 just unsure wether the car would make that power with those modifications? The printout is dated before the engine rebuild so not sure if it had more modifications previous to the rebuild. What do you guys think?

Sorry for all the questions, I知 hoping you guys can help. Thanks in advance