I'm accustomed to this 3.4L engine giving me approx. 30 mpg on the highway (depending on ethanol percentages). It seems like overnight the mpg went from a nice 22mpg in the city to much lower. I'm only getting 225 miles out off a tank of gas now. This is WAY down from the 400 miles per tank I was spoiled on. It's giving me a really rough start... til it gets hot if course. However, the fuel consumption hasn't changed even with a new wiring harness, and a new Delphi remanufactured ECM. Any ideas? The injectors are Delphi and 5 years old as are the coils. Ideas?

I'm guessing having lived in California for a few years because of College...it appears all of the symptoms point to bad injectors. Blue smoke, thinning oil, bucking, ses light, bad fuel economy, a plugged cat (newly replaced), poor start, poor idle, poor general performance...It appears the gas out there ruined my injectors.