[caleb-charles]

If the specification requires MPI as the primary inspection method that is what you should apply unless an approval plan is obtained from the customer. That being said is standard practice to remove all residual inspection materials after testing, therefore no contamination shall be present upon completion.

I would be more concerned that 13%Cr material may oxidize after being exposed to water if FPI process is applied. That type of contamination can damage surface finis and be difficult to remove from threads.