im going with a 4" catback setup. i have 2.5" downpipes which im going to have go into a custom 3" Y pipe then merge into a 4" I pipe. would having 1 4" cutout work well enough in the I pipe or should i do the 3" cutout in each side of the Y pipe?

thanks

 

With a good 4in muffler (such as magnaflow), a cutout will gain you nothing.

But to answer your question, if the muffler did pose a restriction, a cutout in the intermediate pipe would work as well as 2 cutouts on the y-pipe.

 

sweet! thanks for the help.