I added Vance & Hines straightshot slipons to my 07 Lowrider. Should I have it remapped? What are the advantages to remapping?

 

I run the same ones on my 07 street bob, and never remapped. should be ok, as long as you don't have a high flow air filter. Remapping should help with the heat issue, caused by the lean fuel mixture these bikes get from the factory.
you should read this thread https://www.hdforums.com/m_2836828/tm.htm
And also here www.nightrider.com/parts