Few days ago car developed a flat spot at 3k but now has got worse! Plumbed in a boost gauge to see what the boost is doing and it comes it nice and strong but only hits 14psi pulls straight back surges a lil bit then dies to 10 psi. If im driving through the revs the boost doesn't get past 12 psi ish??

I decided to run it through a friends vag com which showed up a lamba sensor fail and also a N249 fault.

Would the lamba problem cause the n249 to kick in when ity doesn't need to? Im going to get a new lamba sensor and by pass the N249 and hope it works but also want to know if this is common as I don't want to rush to change and it not solve the boost issue

Thanks

Nick