EGR Question

[X24]

I have a flowmaster 50 series dual in/dual out muffler with dual pipes. That makes for a very free flowing exhaust system. I also have a superchip and run 93 octane. With these mods my city MPG stayed the same as stock, 16 MPG. Last week I went 600 miles on the highway and got 16 MPG... Something is wrong. Someone mentioned something about the EGR valve causing it to run rich and reducing the gas mileage if there is too much flow. Anyone who can shed some light on this or give me any advice please do so. I would really like better gas mileage and performance. Thanks.

 

[jjue]

yep, I've had my EGR valve stick, causing my computer to go to default mode, and I got 16 mpg on the highway as well. As soon as I fixed the problem, the highway milage went back up.

 

[X24]

You just replaced the EGR valve? Where is it and is there a way to tell if its bad?