I’ve never thought it would be an issue applying plate shaping to the manifold side of the plate edge opposite the groove as well, but I think the key to this would be to do it after the groove is in place, or you could end up placing the groove too close to the closed position.
The thought here, I think, is to get as much air past the plate at the smallest opening as possible, so that the waveform the groove creates starts coming together as soon as possible as the butterfly opens. It might even aid in a larger waveform/vortex pattern being created/maintained at smaller throttle angles. The more air hitting the groove, the stronger the waveform.
I’ve used this twice- once on a 4.6liter f150 and once on a Nissan Titan. It seemed much more effective on the Ford. I started with the dremel’s cutter wheel because it seemed easier to round the sharp edge of the plate off faster, then I “dug in” as far as I dared with the drum grinder. It helped to run a Sharpie Marker around the edge of the plate beforehand so I could judge the evenness of the amount of metal I was removing. I’ve been tempted to pull Wendy’s TB and get deeper into it on my own, but Wendy’s is a bit of a pain to remove because the metal heater bypass tube connects to the threaded stud in the manifold that the TB is secured with. Removing the tube for access would involve topping off and burping the cooling system after reinstalling it, and on this vehicle, air bubbles are a bother to get rid of for some reason.
Then again, more air moving through a smaller opening could make the whistle worse, but it might also shift the frequency into a range higher than a human ear can detect. Regardless, when it’s right, you’ll probably be able to achieve a slightly lower idle speed which translates into better response off idle, when you put your foot in it.
In other news, since I relocated the MAP Sensor and tweaked the MAP enhancer circuit I put on a few months ago, fuel economy doesn’t seem to drop as much as it has in the past when the weather turns cooler and the intake air is denser (more MASSive - air/fuel ratios being calculated by the weight of the fuel and air catalyst). So I think Webdy’s running about as lean as possible prior to installing an EFIE on the upstream O2 sensor to further tighten up injector pulses. How can I tell? I took a longer drive yesterday for work, and the temperature gauge has only read that high in the summer- In the middle to upper range of what the owner’s manual says it should.