GRiSO Intake Manifolds

I ended up stripping the vacuum port of the right intake of my GRiSO. I had been swapping between a pair of cut off bolts (from the PO) plugging the vacuum ports with the stock banjos when I balanced the TBs. I've done this a couple of time this year as I set valves and checked balance while trying out maps from Beetle. My GRiSO with the Zard "race" exhaust  seems to have more vibrations than other bikes in the area (one with the same exhaust).

Back to the intakes. I ended up taking the intake off to helicoil it. That was simple enough, but as an FYI I had to cut 4 or 5 coils off the coil before inserting it so that it didn't extend inside the intake.

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With that done, I cleaned up the intake to reinstall. I noticed that the inside of the intake was rough cast. I thought the factory would have smoothed the air path for optimum airflow.

But on the edge of the boot end of the intake, there was spots machined smooth. It looks like someone took the time to match the inlet side of the  of the intake. It was maybe 5mm wide, but then a small step transitioning back to the rough casting. Is that something the factory would do? Has anyone else seen this on their 8v intakes? Guess I'm looking for other reasons my GRiSO isn't running smooth (beside blaming the mechanic - Me)

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Oh, and on of the intake valve areas looks all gummed up. Not sure why, but will run some Seafoam through it.

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Rough cast inlet manifold is common today, a proven practice in use 20+ years in my experience.
Provides better atomisation, well documented.
The old days of the "port and polish" are gone. Flow bench results saw to that!
The transition blending is also accepted as being correct on production machines.