Hi im building a custom intake plenum for my 2.3-16v and i need advice

Here is my flange.


the problem is i want to use 3 inch pipe to crush at end and weld it directly but afraid of the turbulence of the air flow due to there is 2 ports going into 1 piston.

this is some example i which i want to follow.




What should i do about the access metal at the center of the 2 holes?
Should i die-grind it to make it like a sharp edge? or leave. if i leave it will it affect the flow of the intake?

What is your plenum going to look like ?

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Definitely knife edge it. Ideally you would want more of a transition though. I also think that 3" is too large for your runners. This will decrease velocity too much, especially when it hits the bottleneck at the flange. It would be better to make a smooth transition from the two ports to the single port that would have at a minimum cross section that equalled the total area of the two. So basically calculate the area of the two circles combined and then make your runner the pipe size that has that same area or a tiny bit bigger if you are planning on making very high horsepower numbers or smaller if you are not. This will dramatically effect torque also.
There are also really nice throttle body intakes out there for this engine that you have to hunt for but they have really nice transitions and velocity stacks.
The one my buddy has, has a bolt on plenum so it could easily run with boost.
I am obviously all for making it yourself though and hope this was somewhat helpful. Also, plenum size should be about your engine displacement. A little smaller for more torque and a little bigger for more top end flow.

Its gonna look like a normal box type intake like they used on those JDM engines.