you wont need any bigger than 2.5" pipe any bigger and you are going to lose power with a stock engine not enough back pressure. On my Dakota R/T I have a set of hooker headers true dual 2.5" with flowmaster 40 series dumped at the muffler
I agree with the size, you do not need bigger then 2.5" on any stockish motor. If you had a lopey cam or forced induction maybe. Are you on dakota-durango.com?
I thought I would point out though to clarify things, back pressure is a bad thing, period. The loss of back pressure is not what causes motors to lose low end power, it is the loss of scavenging caused by the diameter of the pipe slowing the exhaust flow away from the manifolds which are extremely inefficient and rely on proper pipe sizing to aid in scavenging. There is no easy/simple way to explain it.
I was on all the Dakota R/T websites then they just stopped samething never changed. My best time is 12.98 1/4
Nice time man! I've run a 14.21 in my 02 4.7L rcsb, that was with HO cams and intake, CAI, Headers, 2.5" true duals, BBK 70mm TB, Superchips tuner, Powertrax locker, 4.56 gears, and 28x9" slicks. www.dakota-durango.com
is still pretty active, got a few on there just to start stuff now, but overall its a good place to get info and pointers for your truck. I'm KotaKid287 on there btw.