Indy car restrictor plate racing

When an Indy car can run flat out through all four corners at Indianapolis because it doesn't have the horsepower to pull the downforce, the NASCAR equivalent is restrictor plate racing. Except in NASCAR it's illegal to back off on the downforce to the point where the car is just as likely as not to spin going through a corner.

Restrictor plate racing is so popular though, isn't it?

NASCAR when they can avoids restrictor plates like the plague.

Not killing spectators is the only reason they mandate them at tracks such as Daytona and Talladega.

The IRL reduced available horsepower through displacement limits at 3.5 liters from 4.0 liters. They also mandate a minimum wickerbill or gurney flap at Indy.