Conference rebuttal: can I add results?
You should check the conference's policy on rebuttals.
In general, you can add results in the rebuttal, but they may or may not be ignored. A rebuttal should be equivalent to a minor revision, not a major revision. That said, there is not much harm in trying as an author to promise more in the rebuttal.

The problem is that rebuttals sometimes promise amazing improvements to the paper, but there is no way for the conference program committee to evaluate the promised improvements before making an accept/reject decision. So the general policy is that authors should ensure that the original submission is up to scratch and not rely on the rebuttal to make major improvements. Reviewers are instructed to evaluate the submitted paper on its own merits. 

In your case, the reviewer has explicitly asked for something -- that is a clear license to provide it. If space allows, you can include that in the rebuttal and promise to add that to the final version of the paper.