There are many things that will cause this , I ran the EVO past 30psi issue free for years with rock steady boost psi
How you have the Vac run to the WG and where the Vac is coming from and if your using delta or internal vac, meaning 1 or 2 vac lines
How and where you have the WG mounted on the manifold
How clean and free flowing the WG mounting is on and to the manifold / piping connecting WG to manifold
How well the piping on the exh side of the WG is flowing and how clean it is
These things are very very important and from what I have found over the years 90% of the problems with boost creep , your not moving enough volume of air with a 2.0 to need the larger WG for the amount of boost your using
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