[AMChrisRose]

Okay, so some more things to check on this vehicle...

Many times, when people install aftermarket long tube headers, they'll accidentally switch the left and right side oxygen sensors, which will result in the fuel trims going .75 on one side and 1.25 on the other. They will be flatlined, and could potentially be the issue that you're having.

Trace the oxygen sensor harness, making sure that there isn't a spot where it could have been melted together or cut/nicked during installation. Also verify that the left harness goes to the left bank and right goes to right bank. It's hard to tell without following the harness up a little bit, because they come down and can usually reach both sides.

Make sure all exhaust leaks are sealed up.

Make sure you use new factory ford oxygen sensors for the front.

Another possibility is that the oxygen sensor extensions for the front are bad. I don't know what headers you've installed, but most long tubes come with extensions for the front o2 sensors, and many times these are bad, causing issues again like you're experiencing.

The rear o2 sensors you can completely ignore. We can turn them off in the tune, if they aren't already. If you get a check engine light for these it will be P0430 and P0420... ignore it for now, if it happens. And we will send you an update to fix it. It will say catalyst inefficiency in bank 1 and bank 2.

The car could be running like crap from many things at this point. You could have burnt up a spark plug by not having proper fuel trim operation, etc.

[papemilio]

My car is running 100% now I can feel the difference with the 4.10s!!! The problem was the spark plugs were bad and a o2 sensor was burnt cuase it made contact with the headers.

[AMChrisRose]

Awesome! That's what I had a feeling it was. Glad you're liking it!