CEL: Lean bank 1 & 2, plus DME says exceeded trim

[Bdc101]

I went on a 600-mile road trip this week, and oddly I got these codes twice during my trip. Fortunately I carry my Foxwell with me so I was able to pull and reset them immediately.



First, about 2 hours in, I got a lean code in Bank 2 (check engine light on dash).



I reset that and then about an hour later I got lean codes in both banks 1 and 2. This time I checked the DME codes as well, and it had codes E3 and E4:

E4 Fuel Trim Bank 2, Permissible Range Exceeded
E3 Fuel Trim Bank 1, Permissible Range Exceeded


I reset these a second time... and then I drove 300 more miles and they never came back. The car did not have any running issues of any kind, even though I drove over 600 miles through temps ranging from 27 to 115 degrees on the same day.



I did a little searching and only found a couple of good threads, most of which were solved by replacing the DISA valve. I replaced my DISA valve and gasket with a GAS unit almost a year ago.


I think the fact that the car ran fine the whole day also precludes any fuel pump problem. The intake elbow is about 3 years old. My best guess is either the MAF is going bad, or there is a small vacuum leak somewhere. I will try to spend a little time looking for a vacuum leak tomorrow.



Any other things I should be looking at, from the more experienced crowd? TIA!