Please help - Just found out my gun be might be E-Cat...
Quickest way of getting legal would be to remove the barrel and action from the offending stock and have that stock stored on a different premises to your barrel and action. Then you can either go buy an a-cat stock and reassemble, or go through the process of upgrading your security to e-cat requirements, and apply for the endorsement.
It's not enough to disassemble your rifle and keep all the parts on hand. A disassembled e-cat firearm is still an e-cat.