I hope you didn't clean the TB.
You've no doubt seen mention here of the "business card trick" - use a business card (sometimes folded) to wedge the throttle place in the position it sits at hot idle. the carbon on the manifold side of the TB will leave a nicely shaded line around where the opening is, and you want to place the groove just downstream into where the dark solidifies.
Does that help?
Yes, that helps. Forgot about the business card trick. Have not cleaned the TB, saw the line where the "turbulence" begins. I may have to add some reinforcement to the outside surface where the groove will go, as it looks too thin to use the big bit. Will keep you posted.
Gadgetman Pellston MI
The following user(s) said Thank You: GregK, Michael Lee
The Hatton to the rescue once again, verifying his Google-fu...
I have a feeling that this “extra touch” hastens the creation and/or enhances the effect/strength/longevity of our Groove when we start moving the plate from its idle position. I believe it came from NASCAR, where they found an increase in torque (or something else beneficial) as I recall.