the Mishnah Berurah states that we say BIZMAN (like Lubavitch) and not BAZMAN in the second Beracha. Yet most of us still say BAZ|MAN. Should we change?

ב"ה Shalom, Your question came to my desk only after Chanuka. The Mishna Berura actually says that in regard to the Bracha of Shehechiyanu , we should say "Lizman Hazeh" with a "Chirek" under the letter "Lamed" and not ""lazman hazeh" with a Patach under the "Lamed". There are different customs in this issue, and most people say "Lazman Hazeh". In regard to the second Bracha of "She'asah Nissim", the Mishna Berura only says that we conclude the Bracha "Bazman Hazeh" and NOT "Ubazman hazeh. He does not mention "Bizman" or "Bazman" However, there are indeed different versions of what to say. According to the siddur of the Yavetz and the Shelah=של"ה, we should say "Bizman Hazeh" in the second Bracha. While according to siddur Otzar Hatefilot and Avodat Yisrael and also in siddurim from a few hundred years ago such as the Siddur of Rav Shabtai Sofer (end of 16th century) and and Sharei Tefila – of Rav Shlomo Zalman Hanau,1687-1746) one should say "Bazman Hazeh". You should not change you minhag, since there are different customs. See: שיח נחום סי' י"ב, נטעי גבריאל הלכות חנוכה, פסקי תשובות סי' תרע"ו :ב All the best