Vacuum leak?
 

I have a 2004 F-150 Supercrew V8. When I took it to Advance Auto the code my truck threw was Bank 1 Bank 2 running lean. Evidently it is better for my truck to run richer than leaner. The tech. there also said I may need to use a smoke machine to see if I have a vacuum leak somewhere or it also may be an electrical problem?

I had to replace my air flow sensor on my cold air intake 3 weeks ago and sure enough that was the problem at the time. Now this new code is reading that I am running lean.

Any suggestions? Will this do any longer term or significant damage if I don't take it to Ford to get it looked at anytime soon?

Any info will be of great help.

Thanks,

Chris