The fixed needle Strombergs will wear the needle and main jet over time. I am a bit confused whether you are talking the early Stromberg with fixed needle and movable main jet or the later with movable sprung needle and fixed jet.
I had a RRC in Saudi that would not meet the ADAC roadworthy until I replaced the needles and jets in both carbs.
I suggest that you fit new needle and main jet as a first action.
Regards Philip A

