Re: V-6 possible mods?
Well, straight pipe is OK, but just run it after the cat converter and don't use a muffler. This will allow you to keep O2 sensors, and still pass emissions. It'll be louder, but you'll mostly notice it in the cab from resonance, as the purpose of the muffler is to eliminate extra noise.
Until my cat-back gets here, I'm running NO PIPE behind the cat on my Durango as it rusted off, and NO shop around town has a replacement, so at least I have a good excuse! I don't recommend it, as I hear creaks and moans from places that I never though possible from having no pipe. It's also dangerous too, as the fumes can get into the cab. My Magnaflow 15659 will be here early next week!!!!!
Intakes are overrated. If you want one, build it yourself. Measure the pipe specs and go to the Home Depot, or where ever, and buy pipe, clamps and such for around $20, then the most expensive part is the cone filter, which can be had for roughly $50. So, for $70 and a bit of work on your part you can have a system that would rival a K&N but costing 300% less. I bought a K&N for my 5.9L Dodge, and mileage did go up, but only if I drive at 55-60mph with the cruise control off. At 65+mph, mileage is the same as with the stock air box.
Some noises you do want to avoid, like running a lower than usual octane of fuel and hammering down on the throttle can lead to engine knock. It's also embarrassing.
'11 Ram Quad Cab 4x4 SXT 5.7L HEMI (stock); 48,500m
'06 Pontiac G6 GT 3.5L 220hp; 64,000m
'12 Chrysler 200 Limited 3.6L 283hp; 28,000m
'99 Taurus 3.0L 2V Vulcan 145hp; 154,300m - Traded
Amsoil in all vehicles!