You won't see much power with the wastegate, but your boost control will be spot on and you should be able to hold more boost longer. Granted I have an ewg from GrimmSpeed, it was the last thing I did.
Also, the up pipe you would have to get to run ewg will pretty much always outflow the stock catless unit. Also, you will see better spool and/or more top end with a set of either PnP exhaust manifolds + high flow crosspipe or a good set of equal length headers. Again, I did the PnP and crosspipe from grimmspeed and I like it. Keeps the stock reliability of the cast exhaust manifold elbows (aftermarket headers are prone to cracking), and the subaru sound. ELH overall offer more power at the cost (usually) of a bit of spool time and the sound of the boxer if that matters to you.
It's not apples to apples since I have the 2.5L, but I hit full boost at 19.5psi at 3200rpm's on the VF52, which is pretty much the VF48 with a different compressor cover to bolt directly to my intercooler. Compare that to stock 13.5psi at 4,000rpm's. We have pretty much the same mods with exception to the wastegate and exhaust manifold.