Financial talk

hi, i have a 1999 pontiac grand am gt, my engine light is on again and its been my 3rd time at autozone for the same problem, the iat air temp sensor code:: P0113, i have replaced the sensor twice thinking it might of been defective but the light still comes on, the people at autozone keep telling me that the only thing that could be wrong is the iat sensor.but i am not sure myself, i also have an aftermarket cold air intake system. could the cold air intake be causing this problem.? i've been told to go to a shop and get it checked out but i dont trust people, i like to do all the work on my car by myself. i dont want to be charged for something thats probly not broken just cuz some guy wants to make some money off me....if someone could help me out, it would be greatly appreciated, thankyou.