Hope im not bothering you, I have a 2004 f150 5.4 lariat. leaving the store jumped in started the truck huge plume of smoke driverside then engine light came on, got home put the CanOBD2 on said P0174 bank 2 ... pulled the Maf Sensor but no damage. any ideas? Maf Is $230----grosss

mine did the same exact thing low idle then get rough and then would shut off. showing lean codes po171-po174. I changed maff sensor, all 4 of the 02 sensors and still lean codes. we sprayed brake clean everywhere looking for vac leak and found nothing until I taped 3 of the tiny red straws together and put it deep between intake and block while running and sprayed and BINGO ran smooth as butter. you can not see that on the bottom in the very back on each side is a 3/8 vac nipple. pulled the intake and found them. passenger side was clean only 1/8 of an inch so the boot was never really on the tube. I put the boot on with a zip tie. I've never been so frustrated trying to find and fix it. I had also changed spark plugs, boots, and cleaned injectors. The Vac leak was the prob. Good Luck

leak
 

I had basically the same problem... guy on here told me to use carb cleaner and spray around different areas of motor till i found the leak... .sure enough... it worked.. found a cracked elbow on the bottom side of the manifold for the EGR valve... 2.00 replacement about every 8-12 months... Good luck!!

This same idea worked for me.