Air Arms Owners Club

I am having a few problems with my second hand s410 classic 2007. The power is about 10ft/lbs with aa diab fields and i would like it a little more. I have fully serviced the rifle and installed a new exhaust vale and new hammer spring. When I stripped the rifle I found the old spring had and extra little spring on it to boot power but it was still under 9.7ft/lbs then. The exhaust port adjuster screw is full out with no obstruction. The exhaust valve spring can not be wound out any more without air leaking out the barrel.
Any help would be appreciated as I am stumped.
Thanks

Is that from a 190bar fill, these guns don't get into their sweet spot until about 160bar, what I'm saying is at 190bar it will probably only be doing 10ftlb but at 160bar it could be 11ftlb +

You probably did this but ensure the hammer rail is polished and free from any oil or grease. It must be dry.
The hammer spring must be the standard one. There are low power springs and hammers.