my dad has a 98 5.4L expedition 4WD and he has been wanting to get a mean sound to it for a while (mainly from hearing my car

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has anyone here bought one of the catback kits and is happy with it, the only ones i've seen are flowmaster forceII (in summit)and dynomax (in jegs) both just a little over 200 bucks, but they dont say what the kit comes with, he'd like to have dual pipes out the back but thats not completely necessary if theres a really good sounding kit that doesnt have duals, what exactly do these kits have?
anywhere else to look? or should i just have him get a single muffler with 2 outlets and have an exhaust shop do the rest?
whats on your guys' trucks?
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88 Notch, B&M Ripper, 3.73's, Ported E7's, Explorer int. w/ ported lower, pulleys, 1.7RR's, full exhaust,65mm TB, Nitto DR's, new best 1/4--> 13.42@106.18 (1.89 short time)