Actually, yes.
I'm Ilkeston way.
1x 1990 K10 (1.2 5spd, very very dead after 232k but probably being used for some stupid project at some point)
1x 1991 K10 (CG10DE conversion, MA12 5spd gearbox being done by Bright Spark Racing-still we're getting it there and it'll be done well rather than...
I can't honestly say I've been paying attention to my fuel consumption.
However, on startup mine splutters oil which sometimes seem to restrict exhaust gases and thus hinder combustion.
Exactly the same issue...
What condition are your valves stems in? The limited revs may be due to excess oil getting into the exhaust valve area and restricting the flow of exhaust gas.
Is it the case that if you put your foot hard down post startup to try and keep it running it will still...