You mean the rubber piece that starts out square over the top of the carb and goes up to the round metal can where the air filter is?
That would be a tough shape, but I think it would be possible to print. However, I don't thing it would be useable unless you have a printer that can print with something soft / rubber like. I can only print in ABS or PLA, both of which are a pretty stiff plastic. Not to mention it would be obvious that it's not original... so if you were going to to that route why not just buy one from a junkyard to begin with? WWWAAYYY cheaper and you're also not out 30 hours of design time and 6 hours of print time...
Just my .02.
I am still working on the bike, got a bit more done on the seat and made a bracket to mount the tail light up. Pics probably next week.