If an agent is interested enough in your novel to ask you to jump -- you yell...
"HOW HIGGGGGHHHHHHHHHH?"
Patrick Rothfuss, author of The Name of the Wind, says that he worked on rewrites for several YEARS with his agent, Matt Bialer, before it was submitted to editors.

so I'm assuming from most of these posts that doing changes without "Official" representation isn't uncommon?
I just keep revising until all the stupid is gone. Having someone looking over my shoulder to help me find the stupid before the rest of your guys get your eyes on it (including you editors) is a very good thing, indeed.
Rewrites are your friend. Agent revision notes are your friend.
I think I'm going to have to borrow that line in the future...I just keep revising until all the stupid is gone.
I definitely agree that agent revision notes are a good thing.