that area just before the manifold dumps into the turbo, the leading edge is about 1/2" thick out of the factory. I ground mine down to almost a knife edge. It does not have any effect on the strength of the manifold at all and allows a straighter line for the flow into the turbo. As it is the gasses take a 90 deg turn, any straitening of that turn will help a lot. The areas that go up against the head are definitely less important than the collector end by the turbo.
Last dyno: 468-rwhp 605-lbs torque(!) On 94 octane @ 19psi
