Johnson appeared on the ``Late Show with David Letterman,'' on Tuesday night, and the host grilled NASCAR's new champion about a penalty his team incurred before the season opening race.

Johnson's crew chief, Chad Knaus, was fined US$25,000 and suspended for four races for making an illegal modifications to Johnson's car during preparation for the Daytona 500.

``They had like a rocket in your car or something,'' Letterman said. ``They actually found, did they find a rocket, a jet engine or something in your automobile?''

``If we could hide it in there, that would be amazing,'' Johnson said. ``That'd be perfect.''

It wasn't quite that extreme. The rear window of Johnson's car had been altered during time trials to change its aerodynamics. Johnson ended up winning the race in a legal car _ which NASCAR is now displaying in its Daytona museum until February.

``Tell them to mind their own business,'' Letterman said. ``And then after you win the Daytona 500, they get the car, don't they?''

``They do,'' Johnson said. ``It's been in Daytona USA.''

``Do you ever get that back?'' Letterman asked.

Said Johnson: ``We get that back, I think the day of the Daytona 500 in '07. So the winner of the event, their car will go in and ours will go out.''