Cannot understand why a fuel filter change would affect anything else. I don't think they ever clog up anyway.
Was there an original problem before the filter change?
The symptoms you describe sound very much like a bad or disconnected engine temp sensor. Works like this: engine cold = high resistance, engine hot = much lower resistance. Therefore if disconnected engine will start normally but will run very rich once warmed up, bad idle, hard to keep going but better at higher revs . I know these symptoms because I have driven my 88 740 with that sensor disconnected. Maybe its not that sensor but I really think you are rich, any black smoke?