I have a theory. Now, I have a 2004 4.6L. I have the aeroturbine on now, but with this set up. Straight pipe 2.5 to Aeroturbine to custom Y-pipe to 2.5 straight back with SilverLine SS 4 inch tips. Well, I was was thinking, to cut the pipes after the sensors, put a 2.5 ID Magnaflow Y-pipe with 2.25 dual OD, then weld a Magnaflow 2.25 X-pipes to that then 2.25 pipes to seperate Aeroturbin mufflers straight to the back. What do you guys think? I want an even flow of exhaust to run through the pipes. Is this a good theory, or am I stupid? Please let me know.

 

I don't understand what you are trying to accomplish over what you have now. Either go true dual or keep what you have. Adding an x-pipe after a y-pipe is a waste of money. The exhaust flow is already equalized from the OEM y-pipe. Either cut out the OEM y-pipe and replace it with a 90 degree elbow and then an x-pipe and dual mullfers/pipes/tips or keep what you have now.