John... if you can get the muffs at the bumper it
helps due to the exhaust being cooler back there...
if you run a X pipe they do work BUT its suppose to
be 1/2 way from the end of the primaries to the muffs
or the expansion point(if no muffs are used)... A
H-pipe you put at the end of the collectors(or close
to the primaries)