Stealth,
I also have an Impact MKII in .25 and I too had really weird accuracy issues. I originally had replaced the stock, 52 mm spring with the 57 mm spring to get more power, (before the power kit was released).
I just kept having accuracy issues..... Sent it back to FX and they told me that the 57 mm spring had broken on the end that you could not see without dismantling.
They replaced with the 52 mm and added the washers from the power kit. I purchased the Power kit to get the Pin probe. And got the Huma Dual TP.
FX got good results at 120 bar shooting NSA 38.9. Speed is around 900 fps on PW4. Recently installed the CF sleeve which has really helped. Thinking about the Harmonic Tuner when I see more results.
So nice to have this gun shooting the way it was meant to after 1.5 years of struggling.
Sorry I'm off topic, just trying to help a fellow discouraged shooter. Good luck.
