x16xe loss of power

[michael squeak]

hi all, a bit confused here :S

ive got a corsa b 1.6 16v, i serviced it last week and started loosing power (http://www.allcorsa.co.uk/forums/#).
it revs up fine on tick over and doesnt miss fire but doesnt seem to pull under load.

any ideas?

things i done so far is

i changed plugs back
air filter back
lfuel filter back

all help appreciated

thanks mike

[John]

cambelt timing ok? I've seen quite a few x16xe's where the lower crank gear spins around the crank under load.