From their Facebook page:

"NAPA announced today that, after due consideration, it has decided to end its sponsorship arrangement with Michael Waltrip Racing (MWR) effective December 31, 2013. As many of you are aware, NASCAR determined that MWR attempted to manipulate race results at Richmond, Virginia, on September 7, 2013. NASCAR assessed a large fine, deducted 50 points from each of the three MWR drivers in the race and suspended or banned other members of the MWR team.
NAPA believes in fair play and we are very disappointed in the actions that led to the NASCAR penalties. We have made NAPAs decision known to MWR and posted a statement on our Facebook page. There will be significant media coverage and discussion among racing fans and we expect that our decision to terminate our sponsorship will generate additional attention. The decision was difficult, but we believe is the right thing to do.
We appreciate in advance your support of our marketing efforts. We will continue to evaluate our future position as it relates to motorsports."

After the hammer came down Michael Waltrip finally decided to apologize. Apparently the cat got DW's tongue. The guy who always has something to say about everything is suddenly quiet.

I feel terrible for Martin Truex and the members of his team. I don't for a minute think Martin knew what was happening but the stink is stuck to him and his crew too. They may all be unemployed through no fault of theirs. Very sad.