FFS - did this have any effect when you fitted it - yes or no! if yes then adjust it - if no then sort it. From then on in then use the bus and take note of whether it ideles eratically or not. If No then dont worry about it. If yes then change it. My guess is it does change the idle which will need increasing and it will stay that way!
did you still need one or are you sticking with the pipe? I dont think there's a lot of difference in fairness but I'm not using it and have sold the carbs it came off.
Can I ... Can I..... Can I resist having a moan about the rubber elbows I bought two years ago to replace the perished old ones on this pipe which in turn have now perished themselves? Apparently not - but god that feels better...