NASCAR Racing: maintaining pace under caution, pace car, robby gordon

Question
NASCAR officials stated that Biffle maintained pace yesterday to win @ Kansas, but that he did not have to keep up with the pace car.  I don't understand.  I know that there is no passing under caution.  However, you must maintain a certain speed, or pace, to stay out on the track (just ask Robby Gordon).  What does it mean to maintain pace if the pace car has nothing to do with it?

Answer
Hi Susie,

Biffle won the race because he was the leader when the caution came out.  He was low on gas, so he had to drive on the apron while turning his engine on/off.  NASCAR apparantly ruled that this was an apporpriate pace car speed.  The rules say that if the car in front of you is going the appropriate pace car speed, you cannot pass him under caution.  Why did nascar not fine bowyer and johnson for passing him? I dont know.
Biffle didn't break a rule.  I think NASCAR's rule should be: If you cross the line first, on the last lap, you win.
Hope I helped.
Coy Jordan