Air handler flue modification

Gas fired forced air furnace in the attic. Newer unit from original and looks like pieces of the old flue pipe have been used to patch this flue together. Is this allowed? Smaller flue at air handler expands to larger flue.

I dont see this as an issue. Is it screwed together or just that metallic tape?

Yeah, thats another issue. No screws and adhesive aluminum tape missing at a few of the seams. Wrote that up, but wasn’t sure about the rest. I know if it went smaller, that would be an issue and this is larger, but wasn’t sure of its affect on drafting.