Gave AKS a call, very helpful. They said they are shockingly expensive and they can get a bit of money off them but still 200 quid each. They did say I've been pretty unlucky here and it's likely not a mechanical failure but injector cleaning won't fully clean them, it only works so well as some crud can get lodged in them sometimes and will never come out. They've got a few reconditioned ones lying around for around 60 quid a pop, still a risk putting them in as you never know but would have to be pretty darn unlucky to find a reconditioned one with the exact same fault if test gives it the all clear.
Car is off to retro resus on weekend for a couple of weeks, gave them a ring and they also have a set of reconditioned ones so worth a go! I'm already spending a small fortune on various engine and chassis jobs this month so if refurbed ones can get me out of trouble for now then I'm happy. New ones would be ideal going forward though I think, whether its overpriced ko3 ones or mapped in new ko4 ones on a hybrid or ko4 setup, least you're getting something for the money by going for the ko4 ones on a better turbo setup!
