I have a 2001 F150 4x4 with the following: Headers, muffler, 4" left, 35" tires. After the header install my engine light came on. I am looking for a tuner that will allow me to control rear O2 sensors, tune and correct my speedo.

 

SCT X3 Flasher with custom tune is your only option, standard flashers wont allow the end user to turn off the rear 02s anymore due to EPA stepping in...

 

Did you check to see what the code was? Installing headers shouldnt make your truck spit any o2 codes or any codes in that matter

 

The SCT X3 is NOT your only option. You could go with an Edge CS or CTS with a custom tune as well. I have the CS with a custom tune and I love it.

Make sure and have your codes checked first though. Putting headers on shouldn't trip your CEL light.