Condor tank

Ok so my rifle is tuned by talon tunes. so the other day it started leaking air and I sent it over to Tony, he fixed the problem but today when I tested the tank out I could not send cp past 850 fps. Before I would send cp out at 980 fps with no problem. I tried adjusting the tophat but the fps changed very little. So I emailed Tony , but in the mean time I was wondering what you guys might think the problem is. My rifle is a .22 condor with 12 in barrel