2000 CHEVY CAVALIER 2.2L

I have a 00 cavalier that i am doing some upgrades on. I have installed a header along with a full exhaust back with 2.25 pipe. Now i am having a problem with my check engine lite coming on and the car running "LEAN". Here's what I had to do, I had to extend my O2 sensor cable because the connection is further then the stock one was. My stock o2 sensor was right next to the motor, now with the new header it is actually under the car on the pipe about 2.5 feet before the cat. Has anyone did this upgrade on this car and ran into this problem? If so did you find out what was the fix for it? I am going out of my mind trying like *** to fix this running lean check engine light on all the time car!

Any kind of help would be very thankyful! I am runing out of ideas and don't hoenstly want to spend more money on bringing it into a dealership for them to repair something i am sure i can do!

Thank you very much Phil from Chicago IL  

hmm, you shouldn't be running lean just by throwing on headers. the problem could be that because you moved the o2 sensor to a different position, so now different readings are coming in confusing the computer. temp and hence composition of gasses would be different even if it is still before the cat. The first thing i would do is actually see if it is running lean. The spark plugs are always a great indicator of what is going on in the cylinder. See if you see signs of overheating, detonation due to a lean mixture. That way you can assess if the problem is bad.  The best chance her is to maybe weld a bung into the header so you can place the o2 sensor in the right place. It isn't certain that that will work but if you have the know how it will be a cheap solution. Another option is a rising rate fuel pressure regulator, this would be a cheap solution if in fact you are running lean.  What do you thing of those ideas?