94 S-10 4.3 Running Rich.... Help

I have been having this on going problem of my blazer running extremely rich all of the time. It triggers the Service Engine Soon light after it is driven for as little as 10 minutes and it usually comes on when you let off of the accelerator. I only get about 12 mpg's (15 tops). The scanner says it is running rich, O2 sensor and maybe the EGR valve could be bad, but I have replaced the EGR valve as well as cleaned in many times, replaced the O2 sensor a few times. I also replaced the fuel pressure regulator and the injector. Checked for loose vaccum hoses and did not notice any. My brother is wondering if one of the return lines is kinked and all of the fuel is being dumped into the engine, so we are going to look at that this weekend. Has anyone else experienced similar problems? Any other suggestions as to what my problem could be?

I have been having this on going problem of my blazer running extremely rich all of the time. It triggers the Service Engine Soon light after it is driven for as little as 10 minutes and it usually comes on when you let off of the accelerator. I only get about 12 mpg's (15 tops). The scanner says it is running rich, O2 sensor and maybe the EGR valve could be bad, but I have replaced the EGR valve as well as cleaned in many times, replaced the O2 sensor a few times. I also replaced the fuel pressure regulator and the injector. Checked for loose vaccum hoses and did not notice any. My brother is wondering if one of the return lines is kinked and all of the fuel is being dumped into the engine, so we are going to look at that this weekend. Has anyone else experienced similar problems? Any other suggestions as to what my problem could be?

Not sure aobut the vortecs, but it could be the MAF sensor.
If the engine is thinking it's getting a certain air mixture, and it's not, it will foul up things, including the o2 sensor.

Have you considered that the computer is messed up?

Heres a link about the CPI, and it's problems/solutions. Theirs a lot of info about the 4.3's here.

http://forums.s-series.org/viewtopic.php?t=2278

Robert