When you use the maximize power metapsionic feat, do you maximize the d20 roll to determine the power DC as well? That is, does the save DC become 20+power level+stat modifier?
Whatever the answer, is it mentioned in some source?
No. If you want to improve your DC you need Heighten Power. I don't know as it's clearly stated anywhere, but it comes down to the Save DC not being part of the "effect" of the power.
