Hi and welcome. First things first I think it would be best for you to confirm for yourself the status of the exup valve so you know what you are dealing with, perhaps the service paperwork is just stating that the exup valve had been removed in order to service it and it doesn't say that it was put back again. Pat's site is an invaluable resource for Gen1 owners and he has a step by step guide for servicing the valve, if you go through the instructions for disassembly you should be able to identify what if anything has been removed and any potential problems in restoring it to proper function if necessary - http://www.cartestsoftware.com/fz1/exupmaintenance.html
You say that you are happy with the bikes performance, if it is pulling smoothly and evenly all the way through the rev range then the chances are the exup is working, however if it is a little sluggish at the lower end and then the power kicks in there is likely to be an issue with the exup.
I hope this is useful, and you'll let us know what your investigations reveal.
You say that you are happy with the bikes performance, if it is pulling smoothly and evenly all the way through the rev range then the chances are the exup is working, however if it is a little sluggish at the lower end and then the power kicks in there is likely to be an issue with the exup.
I hope this is useful, and you'll let us know what your investigations reveal.