I have a 95M 2.0 Turbo Legacy (UK) Its seems to have a misfire when under load. It used to just miss sometimes at about 2000rpm, but now seems to have got worse. The car is only running around 9 to 10psi. It feels to be plugs, any advise.

If it is plugs where from, how much and which ones(bearing in mid that i intend to up boost to 15psi)

 

Check the plug leads, as they do break down under load,otherwise NGKPFR6B plugs are ok to use without any problems.