I have known of people using aluminum based epoxies in aluminum heads to reshape ports etc, but not in steel heads. The only way to build up any part of a steel head is to use nickel welding rod or wire, then reshape it. I would be very leary of using such a thing in a daily driven vehicle. It is doubtful that most compounds would adhere to the steel with the radical temp changes that go in inside an internal combustion engine. Exhaust temps can easily get up over 1000 degrees, causing for a lot of expansion and contraction of materials. I dont know of any compounds that would have the same elasticity, growth, and shrinkage rates of cast steel. It would be a terrible thing to have a chunk come off in your intake port and get sucked into a cylinder.
As mentioned with the aluminum stuff, the only guys I know doing that are drag racers.
Unless the manufacturer of this elixor can show me serious lab tests under the conditions I have mentioned, I would stear clear of it.