it appears Lodgey180 may have misread your post a little. So I will try my best to explain and others can jump in with their opinions.
From what I can gather you are asking why you are
not getting the turbo chatter, but Lodgey must have read that you are getting it.
General opinion is that when Leons make the chattering then it is a sign that the turbo is getting stalled (not good for a long turbo life). Likely causes are faulty DV's or blocked bypass pipes that connect to the DV.
Open cone filters are good if you want to hear more engine induction noise and the DV working. Yes the Bosch part on the right rear of the engine is the DV (Diverter Valve). Most people tend to change these for Forge units or simular as they tend to be more reliable and give a better drive. Also they do give a good noise if you are using a open cone filter. Do a search and you will find lots of info about them.
As far as bypassing n249 I can't
help there as I am still learning myself.