I already have an Apexi N1 muffler and a purple hornie resonator 2 1/4'' inlet / outlet from my old 2200.
I want to put these on a 05 eco.

Does it make sense to put it on the stock piping , or just upgrade the piping with it ?

( i want to try and not void the warranty on the car ) I was told changing the muffler would not void it.

Any ideas?

for what it's worth, change it from the cat back with new pipe, and keep everything else till your warrenty is done with.,

I forget to add , i also have a high flow cat too. Im thinking just change from the cat , all back to the muffler.