truck stumbling. need help

[03stx]

I have been having issues with my truck lately. I am getting a system bank 1 & 2 lean codes, and when I put the truck in park from drive...the truck stumbles like it is about to die then the rpm's jump back up to normal and it idles normal. The only time the truck stumbles or the rpm's drop is when I put it in park from drive before i kill it. I have checked for leaks and couldn't find any. Any suggestions on what this could be?

[whitelightning'02]

Sounds like a vacuum leak to me.....

[L8 APEX]

Vac leak or likely idle air motor going south.

[Silver_2000]

check the tubes under the intake boot

[03stx]

I checked for vacuum leaks the other day and couldn't find any. I am worried it is the elbow on the back of the intake.

[Mark #2]

IAC, remove and clean, see if that helps.

[03stx]

IAC, remove and clean, see if that helps.

I did that a couple of months ago but I will give it another go and see what happens.