I've never tried the Slip 2000 Carbon Killer, but Berryman's carb cleaners are the only products I'll touch for carburetor and carbon cleaning, now.
If you can't locate any of Unclenick's suggestions, I'd recommend Chem-Dip Carburetor and Parts Cleaner (the Berryman's carb cleaner Unclenick referenced). Buying the 96 ounce pail at retail will set you back about $30 - maybe a few $$ less.
Even though I am an absolute fan of Berryman's B-12 Carb Cleaner (spray can) for carbon removal, I think it would be a very poor choice for this application. The primary ingredients in the spray can are: Acetone, MEK, and Toluene. All will leave you feeling "stoned" if proper ventilation is not used. All are very volatile and will evaporate before a decent soak time is attained. And, many people seem to have serious reservations about working with any of those chemicals in today's world. (Obviously, I'm not one of them.
Whatever you do.... I would definitely try boiling it, first.