Ok, first off, as was mentioned, go visit
http://www.durangoclub.com.
I have a 2K SLT+, 4WD, 3.92 Rear, etc. Your first mod should be the airbox, its really restrictive on the D. Instead of just plain K&Ns, I went with the Stage 3 intake from Intense Performance,
http://www.intenseperformance.com, great product.
Then do the exhaust. So far, I've just gone with a Flowmaster
high-flow muffler. Its single-in, dual-out so I have 2 nice big shiny stainless tips out the back of my D, with a nice loud rumble to know its running
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Mesa makes a great set of headers for the D, I think they guarantee ~21 HP. Also, as stated earlier, upgrade to the Mopar performance computer - but do that last, after mods like intake/exhaust. A Bigger TB is also on the list.
If you want to get extreme beyond that, install a supercharger, plenty of advice on the club board on how to do that and what parts you need to change out.
For ride quality, go with Edelbrock IAS shocks. I'm about to put a set on mine along with Hotchkis swaybars (when they get the new bushing for the 2K). I also have 1.5" lift, alloys, 32x11.5 BFG, smittybuilt step/push bars and a power sunroof! I'm mounting PIIA fog lamps on the push bars in another week or so as well.
Can you tell I like to go to Tahoe in the winter time a lot?
Regards,
- Mark