You need atleast a window net. In the 11 second or down to 10's you only need a jacket and proper helmet as well.
I passed tech once then at the starting line they stopped me, and played rules, this was after I passed tech. It was a very minor issue, I say it was track politics.
IHRA is more lax, however if it is a friday or sat night race, with no points, you will get away with more.