I fixed mine by changing out the cold air intake after talking to Mike at Diablo sport. Thanks for all the help. The car runs great with the 91 octane tune and the cold air intake and 3:73 gears runs 13.5 in 1/4 mile no other mods very happy with that from a street car and very few mods.

I have a 2006 Mustang GT with Magnaflow exhaust and X pipe and Modular Mustangs Cold air intake and eng light came on Checked. It has a lean code. I ordered a Diablo sport Tuner installed the 87 Upgrade tune eng light went out then back on still lean code. PO171 and PO174 lean code and P1000. How ...