I've done an exhaust mod for more sound. It's not the same as the post above, in that I just had the center resonator (the turtle looking thing in the middle) cut out and replaced with straight pipes. This makes the truck louder, but mainly only under throttle. It is a bit louder than I expected, but I love it. I'll try to see if I have a video clip, but you can find them on YouTube with the same center resonator mod.
Removing the rear mufflers had questionable results (some said it made little or no difference, others it got really loud if paired with the center resonator removal) and I've run without a center resonator on my other car and loved it, so I went the same route. The center resonator smooths out the engine pulses in exhaust, so you get more V8 pulsing sound without it, but not a lot of extra raspy loudness. Nice growl when you mash the gas and a burble in sport mode when you let up on the gas and coast.
As for the K&N, it DOES foul MAF sensors if you aren't absolutely meticulous about re-oiling. Most who run one on my other car (Volvo S60R) keep the paper filter to use while the K&N is drying. Installing it while the oil is still fresh, putting too much oil on, or not letting it sit for a while after oiling will definitely foul the MAF. Could be that on a turbo car, it sucks more of the oil in, but who knows. Not worth the minimal gains, risk to the MAF, and reduction in filtration in my opinion.
Depending on the design, you'll also be sucking in hot air from the engine compartment, which would likely negate any gains without some sort of baffling.
because my exhaust is still without a scratch.
