Hello, its me again, can you add an option to enable burnt fuel slots to the fuel processor from AAI Industries, cause with the newest version it now has fuel slots and "burns" the fuel to produce the vehicle fuel instead of crafting it from burnable items

Never used that before. Does it accept "chemical" category of fuel, like coal, solid fuel?
If so, the existing option (on "generator-equipment") of this mod should have already covered it, as my script on addition of burnt fuel slots is not selective. It applies to every equipment of the type, as long as it is accepting "chemical" fuel category. So new option or not is not even related to the problem.

Perhaps the problem is from somewhere else. If the equipment is not yet defined when my script on addition of burnt fuel slots is run, it can happen.
As for standard modding practice, new prototypes should be defined in data.lua stage, and changes to prototype properties should be done in data-updates.lua stage. My script is obeying this practice and runs at data-updates.lua stage, so this mod should work with any reasonable mods. (And my mods starts with letter "S", so should in principle be loaded after than majority of mods.)

You may try renaming the file data-updates.lua in my mod to data-final-fixes.lua to see if that works.

I think you have misread my first comment.
It works like a burner assembler with 4 fuel slots, but it has a fixed recipe and consumes chemical fuel to produce one unit of vehicle fuel for every 10 MJ of fuel that has been consumed

Alright, guess I have to crawl into AAI Industries code to find out the type of the prototype used by the entity.
The process you mentioned is a bit "tricky" and different from how the usual machines work, so I have no guarantee yet.
When I have the time, I will check that out.

thanks in advance for looking into it

Just released 0.17.3 / 0.18.2. Please check it out.
The code adds the same number of spent fuel slots as the current fuel slots (4), so the fuel bar becomes very short.
(If it is a problem to you, you have to ask as the author of original machine.)

Thanks, I will test it.
Tested it and it works now, the short fuel bar is no problem for me. thanks again.