I agree with Ian. "Stubs" is too generic, it's hard to find information pertaining to Pex stubs.
A name like "Pex Stubs and Moles" doesn't work either, because users will tend to leave off the Pex part, not knowing it's part of the name. (Just as people do not say "Microsoft .NET", they just say ".NET").
Some name ideas, variants on the Mole theme:
-Counterspy
-Rat
-Burrows
-Defector
Tech, life, family, faith: http://judahgabriel.blogspot.com