I had success getting exhaust stains off my awlgrip paint using a Mr Clean Magic Eraser. It is non abrasive so it won't dull the paint.
I can tell you, from personal experience, that nothing could be further from the truth. Oh, sure, it'll clean. It'll clean well. But it most definitely is
To the OP: If the black stain/streak remover doesn't do it, you may have to make a decision: Live with the black streaks or live with the finish dulled from more aggressive efforts to remove them.
Abracadabra's hull is Awlgripped. We had the same problem and the same decision. It finally got bad enough, by this spring, where we said "Screw it. The dull spots certainly will look better than all these black spots/streaks." So we used that black streak remover, first; then spot-treated with cleaner wax (a BIG
no-no for Awlgrip), then did the entire hull with cleaner wax, followed by regular wax. She looked a lot
better by the time we were done than she had when we'd started.
Someday we hope to get Abracadabra repainted - top-sides and hull. The decks will be re-gelcoated and the hull re-painted with either Imron or Awlcraft.
I'd never in a million years use Awlgrip on anything other than a show boat--that I never actually intended to, you know, use?