Is it any good to put a 66/70mm TB on a stock N/A D16Y8?
I have the ability to tune it to match the bigger TB, but would it get me a little more power?

 

No. It would be a waste of money and energy. Just leave it stock.

 

YES !!! Thank you for the absolutely correct answer.

 

all 102hp....yes, that would be helpful. LOL

 

napkin math:

in 720° of crank shaft rotation all four pairs of 30mm intake valves open by 0.377 inches max. total flow area at the valve seat is 2.79sq/in. per cylinder. there is never more area for intake flow than this since, if there is any overlap (one cylinder closing on intake cycle while another is opening- probably for 15° between each...) neither is near 50% lift much less max lift.

the stock TB has an open area of 3.3sq/in. at wide open throttle (subtracting the area of the throttle plate shaft from the total).

3.3 > 2.79. there is not a flow bottleneck at the throttle body for stock internals.