2004 5.0 MPI
Removed intake manifold from 5.0 MPI for water leak into cyl #1 and potentially others. Found a pinhole leak into #1 intake tract adjacent to T-stat housing. I will be replacing Intake Manifold. Fuel rails and upper are separated from lower manifold. Injectors are able to rotate and move side to side a bit. I can see the rubber O-ring in the hole as well as some rust. I sprayed carb cleaner and toothbrushes one of them, sprayed some silicone lubricant on top of the injector and wiggled it around.

I am unable to pull the injector out of the bore using a good bit of upward hand force. I see no clip to release the injector from the manifold bore. Am I just not pulling hard enough or do I need some kind of tool to leverage it out? There is a bit of rust but I have cleaned out with a brush what I can. I do not want to break anything by doing it incorrectly. Is this just a matter of brute force or am I doing something wrong? I see plenty of vids where people have disconnected the hold downs for the fuel rail and pulled up and most if not all of the injectors come up with the rail so I suspect this is just a situation requiring more force.

https://www.mercruiserparts.com/bam/.../31849/8093/90
I see the O-ring kit part #17 sub assy of part #15. Seems a bit high for a handful of O-rings. Can I just match these up or is there an aftermarket variant of this from the automotive world? Are these injectors a different size or is the bore a different size than the 5.0/5.7 Vortec multi-point efi setup? Assuming it would be prudent to change the o-rings when moving injectors to the replacement manifold.

EDIT- found these
https://theinjectorshop.com/products...5176-280156081
now I just have to get the damn things out, send off for cleaning and re-install.

Contact member articfriends he can provide all the advise and help. Can even clean and flow test injectors

After much scrubbing and multiple Silicone spray applications, rotate, respray, one just simply came out! Just stuck in the hole and could not get out until proper amount of lube and time. Old girlfriend comment in there somewhere? I will be diligent and wait for the lube to do its job.

I just did injectors on 2 v6 mpis over the winter. The injectors were an absolute pain to get out, and some even hard to get in. A few of them to get out I actually lightly clamped a vice grip on for extra leverage.

Articfriends cleaned and flowed all injectors for me. Port motor gained 500 rpm and starboard gained 200 rpms vs. Last year.

500rpms ? Holy crap !!!

The only other thing I changed was spark plug wires. Maybe I fixed a vacuum leak disassembling and reassembly for injectors but who knows. Last year engines would run fine, but starboard would top out at 4000 and starboard like 3800. This year I got to 4300 on both motors with a little Throttle left..
Cruised all the way from Saugatuck to Chicago 2 weekends ago at pretty continuous 3000 rpm with no issues