"... the 120 mph was from when I watched the car go down the track, 120 to 121 was what I watched..."
Yeah, with the NHRA hp police being on duty, at most big races, most of the quick cars sand bag, so their combo won't get a horsepower hit.
A quick search turned up a D/SA speed of 124.06 mph, for Randi Lyn, @ Indy, in August. She was more than a sec under, but had to settle for D/SA class RU. The D/SA winner was more than 1.2 under, which would have earned a hit from NHRA, this year. The US Nats race has been exempt in recent years, but not this year.
https://www.dragracecentral.com/DRCS...r2019#indextop
Look how even the quick cars were very careful to NOT go 1.2 under, this year.
https://www.dragracecentral.com/DRCS...r2021#indextop
At most races, a time of 1.20 or more under the index will get the combo an automatic hp hit.
I've read that some just add a bunch of weight. Some short shift. Some let off early. Some detune. Some use some combination of 2 or more of these methods.
So, Randi Lyn will not be running near as quick as the car is capable of, at MOST races.
Same goes for all the Stock/SS cars that can run 1.20 or more under.