I wonder if NASCAR had of invented roof flaps in 1987, might that have kept them from requiring restrictor plates to limit power at some tracks (superspeedways, the really big ovals) starting in 1988.
Either way, I'm sure they'd be using the tapered spacers by now, so it doesn't really matter if some change might have delayed implementing the restrictor plate (which has since been replaced by the tapered spacer).
In theory lower octane fuel (which would force a lower compression ratio, therefore less power) and/or smaller displacement engines also could have been tried to reduce power.
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