I can relate to your last paragraph. I used to (and still) source dive to find good workarounds to library issues. But I never asked for permission, I just did it. I also delivered on time.

Nowadays, I'm a team lead and I am guilty of telling people "not to go there" (about half the time). It's funny because it actually conflicts with my opinion that I want people to dig in! The choice to "dig in" is a personal risk/reward. It's a risk that an engineer must take while practicing good time management. Asking your manager is akin to making them take that risk for you (the risk of wasted time, passing deadlines, etc).

My crappy advice is... ask for forgiveness, not for permission. If you're a good engineer, you'll come out on top!