It's absolutely spot on, I've done it twice to be sure and that I'm 110% on.

I know out of regrettable stupidity I took the belt off before I tried to undo the crank pulley bolt, on reflection I don't know why.

As a result, I think there was probably a moment where instead of attempting to undo the bolt against the force of the gears/brakes (this is how I normally do it and how I first attempted before I got the flywheel tool as it was stuck fast), I think I must have been turning against the force of a couple of valves maybe?

I mean, is it likely that a valve would be damaged that way?

The only other possibility I can imagine is that maybe the inlet manifold gasket is leaking, or maybe a plug lead is iffy, but I can't see it causing these symptoms.. revs are smooth but I could feel the accelerator pedal vibrating under my foot so there's an imbalance somewhere.

I can't really do a leakdown test as I don't have a compressor :/