Impact power down .

Hi, don't know if any one had this problem with the impact. I changed my seals on my .25 f.a.c. Impact and there was no leaks. But the power is down to 810 f.p.s. At just over 105 on the reg . If I turn the reg up the power goes down. Just wonder if I put the belville washers back correctly.. Any help very much appreciated. 
 
The belville washers in my impact are all in the right way. But there is one washer missing. I don't know who lost it , not me . I can get it to 140 on the reg but the power goes down . Just found something. Before the gun went to a dealer to change the seals the air valve with the four lines on was quite hard to turn , I had to use both thumbs to tighten it. But now I can turn it with one hand. There are no leaks on the gun and it stays pressurised for 24 hours. Any ideas.
 
I changed the seals . There is nothing wrong with them. The reg pressure is the same as it was before. The hammer Spring was tightened up to max setting but when I recharged the gun after it was only putting out 830 f.p.s.. I have the .25 X barrell in as well. The only thing I can see is different is the valve knob before it was pretty tight and I had to use both fingers to move it in. But now it's quite loose .