During qualifying for the Indy 500, everyone references the driver's speed. Drivers qualify based on shortest lap time, not speed. However, average lap speed is calculated as a reference point so fans can have a common reference point.
During the race, Gagné is shown blocking Turbo by weaving left and right so Turbo can't get around him. In the Indy league, as well as most professional and amateur racing sanctioning bodies, this is considered illegal and Gagné would've been black-flagged and brought in to the pits for a penalty. You are allowed one lateral move and that's it, a 2nd move is considered "blocking" and is illegal.
When Theo (Turbo) got sucked into the engine of the Camaro during the street race, he would have ended up above an engine piston, inside the combustion chamber, not below the pistons as depicted. When nitrous was activated, it should have also gone into the combustion chamber, not into the crankcase, below the pistons.
The goof items below may give away important plot points.
During the race before the wreck occurs, Car 40 and Car 41 are blocking Gagné. But between shots. Car 41 changes to Car 42 and changes back to Car 41 during the pile up. While Car 40 changes into Car 3 but some debris from the car is seen in the wreckage.