Rosh Chodesh in a leap year

Below is a question related to the Rosh Chodesh prayer we recite today.

During Musaf of Rosh Chodesh the words Ulichaporas Pasha is added on during a leap year. Why is this done? And what is the significance of it?

...there are twelve terms of request in a normal year (chaim, shalom, sason, simcha ...), one for each month. Leap year has a thirteenth month, so a thirteenth term.

...I just found a Kunteros Achron #448 published on the bottom of the Taamei Haminhagim #448. He writes that the reason we say Ulichaporas Pasha is in case the year was made into a leap year in error and through that we are eating Chomeitz on Pesach.
Read more: http://judaism.stackexchange.com/questions/3153/saying-ulichaporas-pasha-in-musaf-of-rosh-chodesh

Rebbetzin Esther Jungreis wrote about maintaining the spiritual influence of the High Holdays during the year in her two most recent articles published in the Jewish Press. It it worthwhile to read the columns in their entirety.

My husband, HaRav Meshulam HaLevi Jungreis, zt”l, would always make an acronym from the initials of the New Year. What would he have done with taf shin ayin daled – 5774? I feel he would have designated this year T’chey Sh’nas Aidim – “let this year be a year of witness” – a year of witness to G-d.
This is the unique mission that we, Hashem’s royal princes and princesses, have been entrusted with – to give witness to Almighty G-d. How do we do that? Let us start by living in such a way, by arranging our days in such a manner, that whoever meets us will be inspired by our conduct, by the way we go about our daily lives.
Read more: http://www.jewishpress.com/judaism/rebbetzins-viewpointrebbetzin-jungreis/looking-back/2013/09/25/

When I was a little girl growing up in Hungary there were tzedakah boxes in every home, no matter how impoverished; a pushka into which coins were dropped on every occasion. The pushka became part of our lives. In lieu of yesterday’s pushkas many children today are given “piggy banks” – a term that screams self-indulgence: it’s all for me! On the other hand, the pushka teaches that my money is there to share with others – that I save it in order to give it away.
Read more: http://www.jewishpress.com/judaism/rebbetzins-viewpointrebbetzin-jungreis/looking-back-ii/2013/10/03/

A good Chodesh to you.