BROOKLYN, Mich. — The No. 18 and No. 20 Joe Gibbs Racing teams in the Nationwide Series will likely face big penalties after efforts to alter the results of a chassis dyno test.

NASCAR inspectors, preparing to do the tests on horsepower numbers following Saturday's Nationwide race at Michigan International Speedway, found magnets under the gas pedals on the two Gibbs Toyotas.

Tony Stewart, making his last Nationwide start for the Gibbs team, finished third in the No. 20, and 18-year-old rookie Joey Logano was seventh in the No. 18. Those cars have been dominant this year and NASCAR, after earlier dyno tests, took steps to cut the horsepower in the Toyota engines in Nationwide.

This was apparently an effort to keep the current numbers from looking too strong in the test.

"In our post-race inspection — yesterday was the day we were going to chassis dyno cars — our inspectors discovered some shims that were placed on the gas pedal stop," Robin Pemberton, vice president of competition for NASCAR, said Sunday. "It was magnets that were about a quarter-inch thick that prevented the accelerator from going 100 percent wide open.

"The intention was to manipulate the numbers that we get when we get our information and data off the dyno."

Pemberton said NASCAR officials will meet Monday and Tuesday to determine what penalties will be handed out.

"I anticipate that we haven't seen the end of it yet," Pemberton said when asked if the penalties were likely to be severe. "We historically don't make our decisions within a 24-hour period. It takes time to get everybody in a group and talk about it."

Pemberton said J.D. Gibbs, president of JGR, had no explanation.

"J.D. wasn't here," Pemberton said. "J.D. was just going to go back and discuss things with his team. He was apologetic for what happened, to put everyone in this situation."