As the Ish Iti was a 'trvul yom', shouldn't he be avoiding the Kohen Godol both by going to public places and certainly not visiting the Kohen Godol at home
Sholem, UK
The Gemara above 66b states more than this; that even if the Ish Iti was not only tvul yom, but actually tomei, he may still enter the Azorah to take out the goat from there. This is derived from the verse '"Iti"; even if he is tomei'.
In addition, I do not really understand the question because a tvul yom cannot be metamei a person, so why should there be a problem with him talking to the Cohen Gadol? A tvul yom is like a "sheini letumah" (see Rambam Hilchos Shaar Avos Hatumos 10:1) and pasuls food or drinks of tumah. So if a tvul yom visits a friend in his home, he should be careful not to touch food there, but he is allowed in the house.
KOL TUV
Dovid Bloom