I put a power adjuster from Alchemy Airwerks in my 2260 and I've screwed it in as far as I can and still be able to cock it, would that be maximum power then?
Counter-intuitively, sometimes excess hammer-spring tension can be counter-productive. But if you don't have a chronograph to verify, yes, most likely you're at maximum power now.
I shoot a 2260 in .22. It generates 550fps. I removed the power adjuster as it made very little difference to the gun’s output. It may well be that the adjuster was faulty, but I don’t believe so.