P1131 Lack Of HO2S11 Switch - Sensor Indicates Lean
1151 Lack Of HO2S21 Switch - Sensor Indicates Lean
Appears your running lean.
I've seen header/manifold leaks cause a lean code, also I've heard sometimes when you go to LT's you get a lean code.
Also kinda odd but my buddies cobra threw lean codes when the o2 sensor's went out.
check for vacumm leaks and if you can see live data watch the voltage of both sensors, your maf and the fuel trims. the sensors would have not gone bad at the same time, somthing is causing that car to run lean.