Really only clutching at straws here mate but as it's obviously an intermittent issue I would be inclined to think it's associated with the
PCM. For so many different components of the system to be playing up at the same time it must be to do with the electrics and as the
PCM basically controls everything in the car that needs power to make it function correctly (including the power steering) that's where I'd be looking
I have heard also that a faulty
PCM won't always throw error codes when run on diagnostics either, not unless it starts doing while it's being tested :(