So I purchased a FX Impact MKII in .25cal. I love the gun and it shoots well and ive made a lot of kills out to 200 yards. So this is what ive done. I installed a 700mm Superior heavy liner (carbon fiber rapped) also installed Ernest Rowes duel transfer port from 910 air guns (it sits to deep and mag does not go in unless you pull the barrel out some) and i feel like thats not right and the transfer port holes are not lining up right. I installed the fx slug power kit (spring, spacers and ball) and polished everything with 6000 grit (super shinny and smooth). I did not use the slug probe in the kit due to i have already installed the Utah air guns Nielson .25cal slug probe and block (the $79 they sell). I am at 150bar on the power plenum reg and the hammer spring is tightened down to where if i tighten it anymore the gun will not cock. I am shooting NSA 36.2 flat base slugs and all I can get out of the gun is 958fps on max wheel location. Ive messed with pressure ive messed with hammer spring and this is all she has from what i can see. I wanted to be at 1050ish fps for a flatter trajectory at long range. Also i was wanting to get a .35 call barrel and set up but if i cant push a .25cal slug to 1050fps how am i going to have enough power to push a .35cal slug? Am I missing something? Sorry for the long past guys