Tehillim 20

My Siddur says not to say Tehillim 20 on Isru Chag. My Shul says it. What should I do?

Shalom!

Thank you for your question.

There are two issues at play here.

The first is the ban of “lo titgodedu” which is the ban on doing things differently than those around you.

The second is the issue of keeping your customs.

As a general rule, in most such cases, it is forbidden to do something in the synagogue that is noticeably different than the common custom.

However, considering that your custom is not to recite Tehillim 20 (“Lamnatzeiach”) and nobody would know if you recited it or not, you are not required to say it along with everyone else.