I came in off the highway yesterday and at the first light my 06 LC stary d to run rough and I could get any rpm when I gave it gas. At first I thought it was the throttle position sensor. After I limped off the road it died and won't keep running after cranking over. After calling a tow truck she fired up and I was able to drive another 20 miled before having the same problem after coming down from speed into a traffic circle. After ten minutes it will fire up. This morning I'm putting a new gas cap as it won't click anymore so it may have a negative vacuum from not breathing. Also going to put a ecu relay in. Tapped the cats didn't hear anything rattling. Any other thoughts? not lights or anything from the ob2.