@diffs: 4.75 they are
engine: I stripped it completely, bored +0.040, head skimmed, new pistons etc, it runs very nicely
exhaust: collector and downpipe are from the previous 2,25D, this could indeed be reason for not breathing at its maximum
tyres: 235 Black Star Guyane = probably too much profile
Most other hills were taken at first attempt, contrary to some Defs and D1's.
One other steep hill needed 4 attepts after which I smelled the clutch , but that was about 2 hours before this one