It'll take a LOT of tanks of gas to get back what you paid for the intake and exhaust. You ususally look at those for performance, with the added benefit of better gas milage.
A few things you can do which won't cost anything.
1. Run the throttle at a constant speed. Don't pulse the gas very much, use your cruse control on the highway as much as you can and accelerate casually.
2. Watch far ahead, when you see a stop light get off the gas right away. First, you'll coast and not be burning as much gas, second you may be able to coast through and you wont need as much gas to get going again.
3. Try not to turn the car on and off all the time. It uses a lot of gas plus the most wear an engine will recieve is at start up. Your car will be happier in the long run.
4. Make sure the plugs are clean and your airfilter is clean as well. Your computer can more accurately add fuel and set the timing.
5. Inflate your tires up a little more ( BUT DON'T OVER INFLATE!) Just a lbs or two. The car will roll easier and take less gas to move.
6. If you don't need to drive the car when it'* deathly cold outside, don't. Cold weather burns more fuel (you get more power though)
That'* all I know of. If any of the rest of the guys know anything you can throw in some ideas. Those are all the things i know off hand.
You don't get performance for nothing. I have the Supercharged bonneville and man, in the cold weather she eats a ton of gas. But she runs so hard and fast!
'95 Bonneville SSEi - Forest Green Metallic/Dark Tan Leather 136,000 Miles
Mods: Custom Intake w/K&N RX-4750 and custom CAI box, 180 Stat, 24k GVW Tranny Cooler, ZZperformance SC coupler, Sylvania Silverstar (low beams), Michelin Pilot Sport A/* 225/60/16 Tires, RSM Rotors w/Raybestos QuietStop Ceramic Pads, Gold Painted Calipers and Drums, Vented SC cover, Taylor Pro Spark Cables, NGK TR55 Plugs, Red Interior Lights.
Current Projects: 2.5 SC Pulley, Ram Air, Header Wraps, Muffler + Hi-Flow Cat