I noticed that
Prototype Portal and
Soul Foundry handle mana payments differently for their activated abilities. Prototype portal asks for the converted mana cost of the imprinted card, while
Soul Foundry asks you to choose
X, then pay that amount. I think the behavior of
Prototype Portal is more correct, since the rules text states the value of
X, so I modified soul_foundry.txt to more closely match prototype_portal.txt and am attaching the result. I have tested
Soul Foundry with these changes and have not noticed any problems. For good measure, I also used
Strionic Resonator to verify that
Prototype Portal correctly handles multiple imprinted cards, and it does.