.25 Avenger velocities slow

This is my 1st PCP and my 1st attempt at tuning it. I have been watching the AEAC tuning youtube video. When I try to replicate his pro tune for 34gr pellets, I am consistently about 100fps below what he was getting. Is it normal to have that much variability among rifles? Or am I doing something wrong? I am getting ~770fps shooting jsb heavy 33.95gr with reg set to 2700psi and 4.5 turns in on hammer spring. Thanks for any help.
 
Before I did any mods or upgrades to my .25 Avenger, I managed to get the 33.95 grain JSBs to move around 840 fps. I did it by setting my reg to 2900 and turning in my hammer all the way. Forget about being exact with your turns on the hammer spring, none of these guns are consistent between units. Basically just turn everything to 11 for those pellets.
 
Thanks for the input. I tried cranking everything all the way up and I actually got lower velocities! Are there any basic mods that I should be doing to improve performance out of the box?
I don't know if any of it is "basic", but I added a plenum, lightened valve spring, and expanded the transfer port.
The plenum and valve spring are pretty easy drop-in upgrades, and the bump in power is pretty significant. After those two I was pushing the JSBs at over 900.