blow off valve

[Gee]

Hi I have had my Audi a4 avant 1.9tdi diesal remapped it's great but next step is a blow off valve ..can anyone tell me if this can be done .some people saying the computer says it's a air leak and  limp mode sets in .they do sell a 1.9tdi blow off valve  .will this work ..??? Or is there something that we can do ...so the computer would t say air leak ...thanks in advance