[Carpe_Diem_14]

My NOX sensors have worn (warning about wrong ad-blue liquid added keeps appearing), so I am debating about either:
a) replacing them
b) do a DPF and EGR delete, and tune the car.

I have tried the first, with aftermarket NOX sensors I found on ebay (they looked quite good copy of the original), however when installed the car could not recognize them ("Missing NOX sensors" popped in ISTA).

So my questions are:

a) Anyone tried aftermarket NOX sensors? If they had the same problem as me (i.e. sensors not recognized by car) how they solved it?
b) Any feedback from people who had actually made an ABC delete? Pros, cons in real life (not just theory)?

Thanks.

(X5 F15 40d platform)