I think the fact that you can not bet on individual matchups will make the likelihood of someone getting caught throwing a race for betting purposes highly unlikely. As Chris said, sportsbooks run so many algorithms that will flag any suspicious bets made and will forward their investigation to whoever's job with NHRA that is also there to investigate. I am also sure NHRA has someone on their payroll now that will be a compliance officer, this person will probably have a background in gaming/sports betting and not drag racing and their job is to make sure everything is on the up and up.
This whole question on NHRA betting now has me wondering if folks working week to week within the sport have had to sign an agreement in recent weeks stating they will not bet on NHRA races, and I am talking everyone from drivers and crew members to media and support staff. Much like how even a greeter or usher employed at MLB ballparks can not bet on MLB games. On a personal note I will stay away from betting NHRA not only because of my track record on PTWs and Bracket Bonanza but having worked in the past as a media member and knowing a fair amount of folks within the sport I could risk my own gaming license in Arizona if I got in trouble for "inside information". Too much of a slippery slope to risk.