I have a 2002 f-150 5.4 4x4. It is completely stock other than tires/wheels. I have had a single in dual out flow on it. Now i just cut it out and have the cats and a y pipe into duals. It sounds ok but i want something louder/deeper. What would be the best thing for me to do. Can i run true duals? remove cats? what about the 02 sensors ? i would like to run no cats or gutted cats and a flowmaster. What would be my best bet?

 

Cut out the 4 stock cats and add high flow magnaflow cats. You can place one high flow cat on each side of the Y-Pipe between the O2 sensors. The high flow cats will not trip your check engine light and it will give you a deeper, more aggressive sound with your Flowmaster. The cats will also free up 5-8 rwhp.

 

did you have a flow 40? do what Mo Power said but if you want it louder still change it to a flow 10 or cherry bomb extreme (formerly imco extreme) single chamber mufflers. Or instead of mufflers just run straight pipes after the high flow cats

 

If you want a louder exhaust, also plan on getting a cold air intake. It will help the engine breathe easier since the inner pipe is smooth and less restrictive than the OEM intake. My intake made my exhaust tone deeper and louder on my '02 5.4L.