What you are asking is are they letting some people get away with cheating. Think about it. If this were 25 years ago, the answer would be maybe. NASCAR didn't have hundreds of thousands of dollars to spend on checking every nut and bolt. Today? ... NO WAY. Once again. Think about it. Just in the NEXTEL CUP, there are 40+ team owners. Many of them have MILLIONS of dollars tied up in these race teams. Next, look at the side panels, hoods, etc. They are COVERED in corporate logos. Those logos represent MEGA MILLIONS of dollars to these companies. A lot of these firms have full time employees assigned to the cars. Their job? Be sure there is no 'hanky panky' going on ... If a major sponsor is associated with a cheater, that companies reputation would take a tremendous beating... not just on wall street, but on Main Street as well. They would be talking about losing millions of dollars in reputation alone. Last, but certainly the most important are the television contracts. Do you think FOX, ABC, TNT and all their affiliates would allow the media companies to be associated with NASCAR if there were repeated acts of cheating being allowed? These aren't programs like wrestling where the audience KNOWS there is 'questionable activity' being allowed. These contracts are on REAL networks and add up to BILLIONS of dollars.
NASCARs' next concerns are some of these younger drivers like Kyle Busch who grew up with limited formal education and are too dumb to realize how their actions influence younger viewers. How many parents of 10 year kids are going to accept his trivial apology for speeding over 125 mph on a public highway. I know plenty of parents who will nix their kids viewership of NASCAR just because of this. And you think Joe Gibbs isn't concerned? KBs primary sponsor is a candy company! A CANDY company! NASCAR and Gibbs can't let this type of stupid activity go unpunished. And you know MARS has to have their legal departments going over the contracts with a fine tooth comb. A CANDY company!! See why Hendricks didn't fight to keep KB? He is no doubt a fantastic race driver but totally lacks an acceptable level common sense. A CANDY company!!

Excellent answer it seems at times thou NASCAR treeks their own rules a bit or so it seems.