What about bestine? That MSDS doesn't indicate that the brake cleaner is made only of heptane and IPA, it just only declares those two ingredients. It says 60-100% is heptane and 1-5% is IPA. So it might be just those two, but it could also be 60% heptane, 1% IPA, and the remaining 39% unknowns.
Does it evaporate cleanly?