advice

[gt me]

hi i am looking to up the power on my gts-t rb25det spec 1 it already has the following so bare with me/ staight throu hks exhaust with decat /blitz induction kit/profec greddy boost controler /a bigger front mount /custom remap by rsp/ its running 330bhp 280lbt . i am looking into the next stage a lot of the work i can do my self apart from the remaping and initial set up which will be done by rsp ive been told a 1.4 steel head gasket needs to be fitted but would the boost need to be turned down as my turbo is on the limit just some general advice on where to start and what to look for would be very much appreciated thanks