a. Yes, you won't get the maximum benefit without the appropriate map.
b. With the proper map.
c. None.
a) is there a con to running non stock exhaust with no mapping mod?
b) what is the optimal (efficient, effective, economic) way to tune an aftermarket?
c) probability of warranty being void with such mods?
my general concerns here...
grammar, logic, rhetoric... in that order ;-)