Has anyone tried any type of add-on gadgets to increase your vehicles MPG? With gas prices what they are, I was thinking about trying one. But I don't know if I'll just be throwing away my money. Currently getting around 8-9 MPG on my 77 Chevy 350 4X4 4 barrel. Did the tune-up thing, bought all new stuff. Even the more expensive sparkplugs. Adjusted my idle...carb, verified my timing. No misses, it sounds great. Installed transfercase part time convertion kit. Speedometer is off just a little bit ~ 2 MPH at 55. I drove "normal" while trying to figure out my gas mileage, don't really hotrod the truck. About half stop and go and the other half highway driving. Replaced all gas lines, no leaks. Best I can seem to get is 9 MPG. If someone has tried one of these "add-on" for better gas mileage and it works please reply. Actually let me know about your experience either way. Heck I would be happy getting 12-14 MPG. <p>A little more reading if your interested. So everytime I talk about these "75MPG,100MPG carbs that "once exsisted", I get chills down my spine. Feels like the government,oil companies are watching. Been doing some reading on the internet, specially the government patent database. Found hundreds of so called invetions that increase gas mileage, cleaner burning, more horsepower. Have any of you older folks ran across any of these things? The only thing I can think of is the people who knew, some how dissapeared.<br>So, if I post a message stating that I found an add-on or carb......that will probably be my last message I send!