Just bought a KR w/ a 5.4 and was wondering what size pipe to go with on a catback system (shop made) My 97 4.6 had a flowmaster y with a single 3 to dual 2.5 and seemed to lose a little bottom but the sound was perfect. If I do a Catback (without the flowmaster Y ) Should I go with 2.25 duals out to keep some torque? i pull a 4 sled trailer and want the best of both worlds,thanks for your input, Cal

 

I have a 99 with a 4.6 and I am going to put duals on in the next week or so. But with the 3.08 diff. I don't want to do anything to it that will make me lose torque. To answer your question, I don't really know, but I have heard that mangnaflows are best for keeping your torque. That is what I am going to do if I hear nothing else from someone that knows better.