If it is injectors, it would run worse under heavy load, so high revs, accelerating etc. Which fits what you are saying, plus if it is the fuel line breaking down, it could be even though the LP filter is clear. Also LP filters alone arent good enough for fuel injection as they generally arent as fine a filter.
As for the R9 fuel hose, I'd still remove some and check it, there was a lot of fake stuff knocking about, even from reputable retailers! Even though it is better than the older spec hoses, its also still not completely ethanol proof, so will deteriorate over time.