The Mishnah Berurah in 1:17 cites the Shelah Hakodesh, who says that on shabbos and yomtov we do not recite the teffilah of yehey ratzon since we don't bring a nedaveh on shabbos. But is this going on the yehey ratzon of the tamid, and if so how can one bring a tamid as a nedaveh?
The Mishna Berura in 1:17 is referring to the next S'if Katan (1:7) in the Shulchan Aruch.
This can be corobarated by looking at the באר היטב on this S'if; towards the end he quotes the Shela and the rest of the Mishna Berura's quote:
(By the way: I don't see a Yehi Razon mentioned for the Tamid, anywhere.)