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It reminds me of the 81 Cadillac with the 8 , 6 & 4 cylinder mode.
It was called a 8-6-4 engine, a de-tuned big block.
The variable displacement was done by electronic solenoids on the valves along with different fuel mapping when in 6cyl or 4cyl mode.
This guys fuel cut off idea seems very simple yet i am betting it will be very expensive.
I Think a similar effect could be had for $10 by wiring in a kill switch to 1, 2 or 4 of your fuel injectors.