bad gas milege

I have an 89 blazer s10 4x4 with a 4.3 engine.. it has about 150, 000 k on it.. and it sucks gas like crazy.. The dealer said that it had a full tune up and the wires look bran new. Is there anything else that would be causing this. also we are noticing when we let the car idle, it seems to stumble, also we noticed some black smoke coming out of the exhaust when we shoot it some gas.. !! Any ideas !! PLEASE let me know.. thank you!

Pull and clean your EGR with a wire brush and carb cleaner, make sure your pintle is freely moving, pick out and carbon in the egr hole on the manifold. Run seafoam through the system, change your 02 sensor if it wasn't changed with the tune up (probably wasn't). The 02 sensor is one of the most detrimental things to gas miledge. Change fuel filter. Add the EGR mod...(will give you an additional 1 or 2 mpg's on the avg) Go to www.s10planet.com (http://www.s10planet.com) and click on TECH at the top to see how to do it or buy it. Check your timing..(this can also cause bad miledge). Don't hammer the gas, drive like a grandma.. Keep an eye on tire pressure and alignment. Switch to AC/DELCO Rapid fire spark plugs. Add an MSD coil and/or msd 6L ignition system. (this should yield an additional 3 mpg's on the avg) You should avg 15-17 mpg's locally, around 19 or 20.

See if these things help you.

What is this "seafoam" you speak of and what does it do? Thanks.

sea foam is a heavy duty carbon deposit remover... Available at NAPA or Advance auto parts