An aside, using vacuum (negative) pressure to control fuel delivery through a carburetor is not a new concept. The original Ford/Lincoln Electronic Engine Control (EEC) I system on the 1979 Lincoln Versailles. That system used a 7200 Variable Venturi carburetor, which was the same as the 2700 VV carb, except the 7200 VV used EEC I vacuum to control how lean or rich the A/F ratio was, with an Oxygen Sensor with a MAP sensor to control how much vacuum was applied to accomplish the proper ratio for emission control purposes. It was a kluzty setup compared to later Electronic Fuel Injection (initially via Throttle Body injection, and later Ported Fuel Injection). But, it actually worked fairly well, although diagnosing intermittent problems was difficult as the EEC I system had no onboard memory containing error codes. The Rotunda tester was useless for diagnosing intermittent problems as all it did was let us put a dummy load into the system fo various sensors. Gee, what else could possibly go wrong with all that elaborate equipment? heh heh...
I actually liked the 2700, and even the 7200 VV carburetors. I like the simplicity and reliability of the 2100 and 2150 2v Carbs more. But, when set up correctly the Variable Venturi carbs were really decent carbs, even if a little temperamental at times. They were the interim step before Throttle Body fuel injection was finally introduced. That said, they were not better enough for me to want to convert 2100/2150 carbs toa VV 2v carb. But, if I had a car with a VV carb givig grief I would be tempted to replace the VV with a 2100/2150 carb as opposed to rebuilding or replacing the VV, especially if it was using an old EEC I system. The 2100/2150 carbs are more simple to rebuild and adjust, and are more reliable in the long haul. That said, I have not seen a car with a VV carb, much less an EEC I system for decades.
Anyway, the vacuum controlled A/F adjustment approach can definitely work well, and I am glad to see someone is actually doing it as a retrofit solution. I just hate to change what works so well for our Mach 1 and install the Carb Cheater until I see how it has worked out for others who jump in early on. It is so nice to already have a nice running engine with its Holley 750 Vacuum secondary throttle setup that is working so well as it is. That said, I have the Holley running just a tad on the rich side, nothing excessive - just enough to ensure I am not running too lean under any conditions. Hell, it even cold starts nicely and runs well while warming up.
