If your average is 14mpg with a 3.8L and you're not hot rodding it, I would highly recommend doing regular maintenance because that is pretty low for a 3.8. I used to get around 18-20mpg with my 2000 around the city. Install the CAI, change spark plugs, wires, fuel filter if you haven't already. Clean the TB, at least until you get a new one. I would start there for the MPGs. As for power adders, the CAI won't give you much gains, but will help. As mentioned above, I would invest in a tuner. This will probably give you your best bang for the buck and some have also seen an improvement in MPGs. This way, you have the tuner handy when you add other mods down the road. I have the BAMA x4 from American Muscle and I love it! Mostly because of the free tunes for life. Goodluck!
Procharged D1 on 12Lbs, MPT 93 Tune, 73mm BBK TB, Ported Upper/Lower Intakes, BBK Shorty Headers, FRPP Cut n Clamp Xpipe, Borla S-Types, Barton Short Shifter/Blowfish Bracket, SS Clutch Line, Whiteline Trans Bushing, One Piece Driveshaft, Front and Rear Tower Brace, Whiteline Front and Rear Sway Bars, Whiteline Adj LCAs/Adj UCA, BMR Relocation Brackets, BMR adj Panhard Bar, Eibach Sportlines, FRPP Dampers, 20" AMRs, 3.55 gears, Brembos