Can't see how it's running a std chip with that boost, I wouldn't worry about the boost at the mo, just take it easy.
Did the specialists offer any explanation as to why the gaps in the rings they say are the problem mysteriously correct themselves on left handers ?
It sounds like you may have major fuel starvation, being classically better one way than the other(corner wise).
I really would start with the basics, look at the chip and see if anything is written on it to identify whose it is, then you'll know what spec this is meant to be used for.
I assume, as you need it that you have a modified breather system, with 24psi, can't say what power it might be, but would expect it to need to be nearer 380/400 to feel faster than a 331bhp 2wd.
If you're taking the engine out, I would do a compy test first, this won't show up leaky oil control rings but if others are shagged it needs doing anyway, rather than just plonk it in another car and hope for the best.
It would then need a serious looking at, preferably on RR, do all the basic stuff yourself, ie fuel pressure check gaps etc.
tabetha