Welcome!!! Excursions are a great family vehicle... We have 5 kids, and make use of ours daily... it's my wife's primary vehicle. Ours is 4x4, so the fuel (not gas!) mileage isn't as great as yours might be, as it has less weight to drag around being 2wd. All 3 of ours get about 12-14 MPG, with mixed driving, mostly around town and West Virginia hills and back country roads. Best I've gotten is 16 MPG from the red truck when I took it to NC about 2 years ago, and kept the speed down... 60-65 MPH is the sweet spot for mileage.
Like they stated above, the DIY intake/6637 filter mod is the most cost effective intake/filter out there, install takes about 15-20 minutes with basic hand tools. It's the first thing I do to a 7.3 PSD! Next, ditch the stock muffler, it's the bottle neck in the exhaust system. Either straight pipe it, or install a straight-thru style muffler, the sound increase is minimal. On my straight piped trucks, I do run a chrome exhaust tip, but it has some small baffels/glass-pack style packing in them, and it takes the edge off the straight piped sound to the point that it's not objectionable at all, and even without, it's not too loud.
Get some gauges... Boost, EGT, trans temp, are a must-have. Then a quality chip with some custom tunes. I like DP Tuner, have them in both trucks, and picked up loads of power driving the way I always do and get the same mileage, or if I can keep my foot out of it, gain about 2-3 MPG across the board. I can't keep my foot out of it... I drive with the passenger side window down (even in the winter, at times!) to hear the turbo whistle from the straight pipe!
Post up some pic's of the new ride... welcome to the fine family of Excursion owners!
'99 E350 DRW Stahl 11' util box van, 7.3 PSD, stock. 138k SOLD
'00 F350 extcab, 9' utility bed, dually 228k
E'99 F250 extcab, S/Bed 211k. Sidelined due to motor issues.
'00 Excursion Limited, 7.3PSD 294k
'84 Chevy K-30, 6.2L TD, woods/trail beater. 141k
Last edited by dieselcrawler; 01-01-2013 at 12:39 PM.