These seem like contradictory positions....just sayin'.
The rules are the rules, whether they're actively or intermittently enforced. For those that show up expecting to play by the rules, it is damaging for cheating to occur, whether it's called out or not. It's damaging for the sport to have such a philosophy. Either people have a regard for the rules, or they're not playing the same game... Are people of low morals willing to do "whatever it takes" to win? Yes. Should it be encouraged? No. Really, I'm surprised that you even mention a prevailing philosophy of "it's their business what happens once its' sold...." Sure, it is.
But if you're aware that people are cheating up stock classes, for the good of the sport I'd be making their local tracks and tech people aware of it... Or at last blasting it out on Bob's that it's likely so that the racers can seek confirmation and accountability... This is also why EVERY track should have a competent and well-trained tech-person with all the tools available to check at least the major performance gain areas... It's human-nature -- people will cheat to unfairly gain rewards, in the absence of fear of consequences.
To the original point of getting rid of prep.... Once we address the issues of why prep is happening, and solve that, it's not likely to go away, unless the karting participants see unequivocal proof that it isn't needed.... Or a parc ferme is instituted.
