This is more a matter of how the phrase should be read, as jargon, and not how the phrase will be (mis-)understood by the general public in casual conversation.
As a writer, if you can't count on a technically-minded audience, you're (unfortunately) best served by avoiding relative multiples entirely, as well as relative percentages at or above 100%. Unlike "two times faster" or "330% faster", there is no confusion, generally speaking, about how to read "three times as fast" or "430% as fast".
As a reader, in the absence of evidence of the author's intent to the contrary, if you encounter the phrase "X times faster" or "X% faster" I believe you should treat it as equivalent to "(X+1) times as fast" or "(X+100%) as fast".
I understand that linguistic relativism is in vogue at the moment, and even agree with it to an extent. The point of having language is to communicate, after all, which implies that the meanings and customary use of phrases are not fixed in stone; they change depending on the speaker, audience, and context. However, by the same token, I think prescriptionism is warranted in cases like this one for the sake of preserving our ability to communicate clearly and concisely. Ambiguity serves no one, and we don't need another inconsistent way to say "X times as fast", whereas maintaining the regular structure of the language ("X00% = X times" and "X faster = original speed plus X", regardless of context) helps to reduce the reader's cognitive load, leaving more energy for the real content. While there is no inherently right or wrong way to design a tool, some tool designs are more fit for purpose than others, and the same is true for the tools of communication, i.e. languages.