Exhaust Issues

[Maxtini101]

I'm having issues with my engine light coming on with "p0171" "Air Flow Meter Bank1"

I do have a custom exhaust (Graham Goode CAIS) and a Primary Designs Maniford & System on the car.

I have replaced both Sensors which seems to cure the problem for about 5/6 months. Do anyone else have this issue and now how to resolve this?

I am selling the car next month and will be installing 2 brand new sensors in the car to try and cure the issue.