Looking at maybe changing turbos

So my 08 hatch wrx is running 320bhp with a vf52 turbo and other mods.i have read that the vf52 is at it limit at 320bhp but i would like to get to about 350bhp.but i thinking of something a little diffrent for my wrx.so what i had in mine but would like to no what the turbo is good for is maybe going twinscroll with a vf37,are they good for 350bhp,i read vf36 is better as spools faster and is ball bearing but does same bhp as the vf37.i no i need to change headers and stuff as well thats ok.i read on the 2.0litre you need to change the sum to fit the headers.but on my 2.5 will i need to change sump as mine is equal lengh headers anyway.

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