lOOKING FOR HELP. i have a 2003 f 150 5.4 4x4. I need new exhaust. im going to be doing a complet system from headers to tips. I want to get ride of the Cats, open up the system. I want to do a true dual exhaust system mufflers of choice is Magnaflow. with getting rid of the cats, HAS ANYONE USED O2 SIM, AND WHAT BRAND DID YOU USE, and where did you get them?( i see jeggs has o2 sims but thay only go too 2002 for f 150s.) i know the only ones that i can take out are the fare back ones, i know for the engine to run right the front two need to stay. the next thing can i open up the system? what about back pressure? i may be nice to the enviroment and at least get one pair of high flow cats. email at ( ridersofthestorm680@yahoo.com )