Yeah, I've run into this a few times. If your headers are chromed, I'd recommend using a plastic ice scraper to get the big parts off. Then use some chrome polish after that. I can't promise you'll get ALL of it off, but it should work OK. If that doesn't go, you may have to move to a metal edge piece, but you run the risk of scratching the chrome finish, and that could lead to other problems in the future.
Another alternative is to find a heat gun (used to remove paint from walls, and on heat shrink tubing) to cook most of it off. Again, I can't say it'll get all of it off, and it may damage some painted pipes, but it's worth a shot.
Hope this helps.
Luke M
Used to have a 1979 CB750L, sold it as a parts bike, now riding a slightly modified 1984 VT700C. Network/Field Engineer. Central OH, USA, Earth, Sol System, Milky Way Galaxy, Universe.