I know a few people got popped in the state of Indiana over the last year or two for doing it, and they should have been. Transmission fluid was even used to soak them in one instance that I can remember. The only way to ban it completely is go directly to Hoosier, and American Racer, and durometer 20 tires each, and get a range that it should be in. If someone rolls out with a 35 on the right rear, and it durometers out at a RD12, then you have a problem. Teching this isn't difficult either, do it before the feature, that way there is no complaining about the "tire being to hot" after the feature.
That's just the basic soaking though, there isn't a way to check at the track for the good stuff all the professionals that cheat use. After the World 100 feature at Eldora, they pull the top 3's tires, along with two randoms, and send them off for chemical analysis as the durometer test doesn't work, because it doesn't change the actual hardness of the tire, just how fast it comes in, and how long it can control that temperature. You aren't going to stop that kind of cheating on this level no matter what you do. But in order to do it, someone really has to have the equipment to do it right, a rotisserie, the proper rollers, and the right technique, and before anybody asks, I've never soaked a tire in my life, but I know of a few people that have done it before.
I have said this for years about Powri, but nobody seems to listen to me. Powri's goal for the micro sprints is to pay for the midget races they have, just like the Shootout is for no other reason than to pay for the Chili Bowl. I cannot blame Powri, and i've only been to a couple of their shows, but they are very well run, and they pay OK, but they do not under any circumstances have the "best interests of micro sprint racing" in their minds. If they did, they wouldn't allow 2 Mil Kawi 636's to run, along with 2 Mil Suzuki 750s.