While the VW scandal is based on facts with hard evidence [1], your other theory is currently conjecture. [1] https://www.newscientist.com/article/mg22830414-

While the VW scandal is based on facts with hard evidence [1], your other theory is currently conjecture. [1] https://www.newscientist.com/article/mg22830414-800-how-did-volkswagen-cheat-in-tests-and-can-it-fix-affected-cars/ https://www.newscientist.com/article/mg22830414-800-how-did-... "Volkswagen programmed its on-board software to detect when cars with its TDI diesel engine were undergoing an emissions test, using information from the steering, brakes and accelerator. It then tweaked the engine settings to minimise levels of nitrogen oxides (NOx)."