The funny thing is that NASCAR doesn't know what they are looking at half the time, but anything that looks "odd" will get banned right away. So as long as it looks like it should be there, they won't know the difference. Nothing cobbled, it's just discreet.
They also don't like one manufacture making significantly more hp than another. So what we try to do is all find power at relatively the same rate. If say the Toyota motors make a good amount more horsepower than the rest of the field after a race, they might change a specific rule that will only affect them. They did this in the Nationwide series last year. It really sucks because we're paid to find horsepower and it's like punishing us for doing a good job.
But really other than driving, there's nothing else I'd rather do.