www.o2simulator.com check this out if you want to get rid of cats with out a code.

how do u install these and on which o2 sensors, pre-cat or after?

http://www.mikefordmustang.com/write...e_files/O2.jpg x-pipe

just so you know there are no more HP gains in an X-Pipe over an H-Pipe and if you want pre muffler exhaust add dumps.

after cat they have instructions on the site.

i cut the cats off my 1997 almost 2 years ago and the check engine light has been on ever since... but the added HP,torque, and maybe 1-2 mpg makes it worth it.. sounds like a beast with 2.5" tubing, true duals w/ flowmasters .... THE MONSTER SNARLS KEEP THE NEIGHBORS AWAKE!!!