The variable intake on the cars is further up stream and does not get the extreme fluctuations that the truck system gets.
This only means the system does not fall apart, it in no way means it has one cent of value. Having driven over 100 K Miles in hilly country with these engines the best I can tell the variable intake was installed to reduce torque. With a SOHC the engine would not make enough power to climb a hill in high gear at 26 - 2800 rpm so you had to down shift to get over 3000 to open the intake. Once I eliminated the variable intake I could torque up hills in high gear and saw a consistent 2 mpg improvement in mileage.
When I installed a DOHC engine, on my first drive I found the intake opened at 4500 revs, Flukin useless. Without the variable it pulls hard from 3200. I also now see 28 mpg in my Diamante wagon with the DOHC and 5 speed, not bad for a car that got 22-24 stock.
Maybe if the variable intake was controlled with MAP and RPM it might have value but RPM only is a stupid engineering mistake.
One other item with variable intake on the cars is that it uses a position sensor, when this goes bad it smokes the 5Volt supply from the ECU. Guess what, the engine needs that 5V power to run! I have a bad leg, I like to limit my walking to when I want to walk.
As far as Franks application, he has a good intake for what he is building. Even Mitsu did away with the variable crap on the DOHC Turbo engine.