these past few days i have been getting a code po171 and po170, it says bank 1 is running too lean!

i have a greddy turbo s2k that has been tuned for 5 months now. i try to clear the code, then the car just runs fine, but today i cleared the code and the car is idlling in neutral low and it randomly turns off.

i checked for vacuum leaks, exhaust leaks and gas consumption is as usual.

how can my car change from one day to another for being tuned to running lean...