I've just serviced my pikes after they locked up.
Replaced all the seals and the correct amount and weight of oil in each leg.

However they now need a load of effort just to compress them,there's no sag in them at all when I'm on the bike.

I'm running them with only 100 psi instead of 150, but there's no difference.

Any ideas what could be the problem with them?

Sounds like the fork is locked out…

Had similar with a blown Motion Control seal, maybe the seal wasn't seated properly?

They're not locked out, there is travel, just takes effort to get them started.

dual air?

Yes 454's

did you use the correct size of o-ring and did you make sure that the foam rings didn;t get twisted at all as you put the lowers back on?

Cycle each part of the fork separately to work out which bit is sticky