turbo boost drop. help!

[brent 3045]

car been on rollers today and after 5k the car dies and boost gos to .3bar, only fault code i have is n249 mechanical malfunction but i have the n249 bypassed. with the n75 connected the boost drops after 5k and with it disconnected it boosts more. car has stock map on, relentless mani, 3" all way thru with decat , green cotton panel, cai, large port head with transition, n249 bypass, oil catch can turbosmart recirc valve. any ideas? am struggling lol

 

[camscockle20vT]

Sounds like a leak to me if the bypass is all plumed up properly. Best check all the pcv pipes around the inlet manifold and to the bypass.

 

[brent 3045]

have checked all, had it pressure tested today and no leaks. hoses around manifold are fine too, uprated them with silicone ones
also got post cat lambda fault code but i have a decat, would this cause issues?