Metal Trigger Box Issue...

Hello fellow snipers.. I recently purchased a metal trigger box for my MK96... I was excited to say the least due to the fact the stock one was falling apart.. However, upon chrono check-ins yesterday before a scenario game, I realized the trigger had taken 125 fps away... Not to happy about it... So now what do I do next?? Is there any way to get the fps back I once had?? Or do i need to upgrade my spring?? Which I already have.. Is there a certain part in the trigger mechanism itself I need to replace and or adjust?? Any info or input will help.. Happy sniping