if you search a lil, there was a huge discussion on here about the back pressure myth. you may wanna look that up before you start cutting. it has some links to articles about this subject basically stating that "back pressure" is not necessarily needed.

 

where can i find that discussion ???..i searched and came up blank

 

myth: u dont need it

 

on this site.
https://dodgeforum.com/m_622780/tm.htm
https://dodgeforum.com/m_403116/tm.htm

another good site.
http://geocities.com/butlerspeed/exhaust.html

in case you care what ricers have to say about it.
http://www.hondacivicforum.com/m_39893/tm.htm
http://www.team-integra.net/sections...p?ArticleID=48
http://www.team-integra.net/sections...p?ArticleID=16

and just in case that wasn't enough, a vid!
http://youtube.com/watch?v=_7rZ-wrfPfs

hope this helps.