Find a different kind of stimulation
The past tense of "whet" is "whetted."
So: "The speech whet his appetite" is wrong. "The speech whetted his appetite" is technically correct.
But it sounds terrible and is cliche to boot. Here's your chance to do humanity a favor.
And I'll take this opportunity to issue a reminder: If your interest is "piqued," it's not spelled "peak" or "peek."