lakoe

So to start, i have a 2008 Audi s5 with the CAUA 4.2 v8. It has 100k miles and about a month and a 1/2 ago it began getting misfires in cylinders 1 2 and 4, so i went about diagnosing and checking the plugs and coil packs and it wasnt them so i moved to injectors recently and took apart the intake manifold, pulled both fuel rails and replaced the 3 injectors on 1 2 and 4 and replaced the left sides o rings but not the right injectors o rings. i also didnt replace the teflon seal or the intake manifold gaskets when putting it back together, so i finally get it all together and the misfires on 1 2 and 4 are gone but now its cylinder 5 along with a lean code

(whats different from when i bought the car - cold starts are a lot quieter, doesnt scream like it used to, much slower, almost sounds muffled when its straight piped, feels like its running on 5 cylinders not 8 and lastly
when i do a pull above 4k rpm, a flashing engine light comes on for 5 seconds and then goes back to a static engine light)

only ideas i have is to take the whole manifold off once again and replace the other side of fuel injectors o rings, and replace the two intake gaskets.


TLDR - 3 misfires, replaced injectors now all 3 misfires gone but new one on different cylinder and lean code. drives the same before fixing.