Originally Posted by SumAmerican

the lag your getting after 55 is probably because you changed the size (back pressure) of your exhaust system. The more back pressure you got the better torque you have and the easier it is for the D to pull anything.. You have a few options if you wanna get back some of the torque. A good tune up is always very good.. I pull a 4000 lb boat around every weekend or so and I found that my least favorite upgrade did the most while pulling the boat at highway speeds.. That upgrade was putting on a taller intake manifold which moved that durango's power curve from stock 0-2000 rpm to 1500-3500 rpm.. those are manufactures stats so a good chance that they're bull but the best upgrades for any power and torque on the D is easing up the intake system..

I call the intake my least favorite because it was expensive as all heck and actually hurt city driving mpgs. but i got more power!