A couple months ago my truck gave a cylinder 1 misfire code where I swapped my coil with cylinder 3 and when it came back I got a cylinder 3 misfire code, so I replaced that coil and it drove excellent until yesterday.

I once again got a cylinder 1 misfire code, which I thought maybe the sparkplug is damaged causing these coils to short? So swapped the coil with cylinder 2 now to see if the code would follow again. When I drove it this time it would still rattle but not the same as a misfire and finally threw a system too lean bank 1 fault. This being weird that the misfire went away but hard to characterize the issue. I also notice that when I am parked the truck seems to run smooth but when I shift into drive the rough idle really shines.

I am suspecting this is some sort of vacuum leak issue but have sprayed brake parts cleaner on various hoses of interest and not getting any engine RPM response though not sure if I hit all the correct hoses or the right spot. Has roughly 160K miles on it and believe all the vacuum lines are still factory. My under-hood schematic is smeared/unreadable so not sure where to start with replacing or what to replace there.

 

Welcome to the forum.

 

Through the years ive learned most vehicles need a major tune up after 150,000 miles. It's at the mark where a lot of work needs to be done.
first consider clean the grease and grime away from the schematic and motor with some heavy duty engine degreaser.
​​​​​Sonetimes the oil can leak into the plug wells, that can cause all kinds of problems.
What type anti-freeze in it? Was there a milky color in the oil? Maybe it's a head gasket, or and intake leak?

 

Using brake/carb cleaner to check for vacuum leaks isn’t a reliable troubleshooting method.

Use a smoke machine—or build a simple one yourself. I made one using a hand pump from Harbor Freight and cheap cigars from the gas station. Usually takes about three cigars before the smoke starts coming out from the leak.