Suggestions For Beefing Up A New Gm K2500 6.6 T/d

[GasCan]

Just bought a new Turbo Diesel GM and it's being lifted this week. In addition to the 4" lift, wheels, flares and a few others odds and ends I am also thinking of beefing up the performance. While my wrenching days are all attributed to carb fed small blocks, this stuff is all new to me.

 

I have come to learn the newer GM's have particulant filters and have been told this kills the mileage. If that's the case, what is the first thing most do to gain some mileage and power without killing off the warranty on a new rig? Also, is the Turbo Diesel with its Allison 6 Speed Trans effective at running 33" tires when equipped with 373 gears?

 

The trucks being used for daily commute plus business travel with the odd trip to the mountains to play and camp? Thanks in advance!