The words of crew chief Mike Shiplett were one of the incriminating pieces of information NASCAR gathered from the No. 41 team after Sunday’s race at the Charlotte Roval that led to Tuesday’s penalty.

NASCAR started reviewing data immediately after the incident was called into question. Custer slowed on the backstretch on the final lap going into the chicane, which allowed teammate Chase Briscoe to pass multiple cars as he fought to advance in the Cup Series playoffs.

Among the data that NASCAR looked at were braking, steering, throttle and all audio.

“The data was pretty telling,” NASCAR senior vice president of competition Scott Miller said, “and then when we got to the audio and had the crew chief telling the driver that ‘I think you’ve got a flat, checkup, checkup, checkup’ when he couldn’t even see the car or have any idea whatsoever that the car might have a flat, obviously pretty telling as to what went on there.

“That, coupled with the data and the video and all the rest of the things that we looked into — that was the bulk of the things we looked into — nothing contradicted the fact that was done deliberately by those individuals. So, we were certainly forced to react. We can’t have teams manipulating the finishing order. Certainly, we’re on super high alert for the playoffs, and had this been the determining factor in the 14 [Briscoe] making it into the Round of 8 or not, it certainly would have been bigger.”

NASCAR stated before the formal investigation began that it will not change the Round of 8 playoff grid, and Miller acknowledged on Tuesday that Briscoe would have advanced without Custer’s move. There was also nothing incriminating found on Briscoe’s team radio about needing help from teammates.

“Involvement over the radio and instruction of the radio that could not even be construed as anything else, those are the things you can’t overlook,” Miller said. “Could we call it teamwork? Yes, teams work together, they draft together, they do all kinds of things together and work as a team, but blatantly pulling over and changing the finishing order on the last lap is what makes it over the top and especially with instruction from the pit box.”

Miller admitted that NASCAR discussed suspending Custer as he was driving the car and listened to the instruction. But in the end, Custer was fined $100,000, and his team docked 50 driver and owner points. Shiplett was fined and indefinitely suspended.

“Probably a big reason for (not suspending Custer) is really kind of super flagrant things that eliminated other competitors or actions that were just completely unacceptable,” said Miller. “Not that this one was acceptable, but [things that are] dangerous, other things in [that] nature are the only things that in the past we’ve sat a driver down for.

“We did consider that, and we opted not to because of the past precedent that we’ve set for sitting drivers down. It didn’t feel like this completely fit into the pocket.”

Stewart-Haas Racing is appealing the penalty.