I have heard that the only difference in exhaust mounting between the 401 and the 17+ Duke 390 was regarding the slip-on being lower on the 401. I also checked the Competition Werkes website and the part numbers for the cat and canister delete pipes are the same for the 401 and 390. So in theory it could work.
However, this is what LeoVince had to say:
“To our knowledge only the cat eliminator that we offer for the Vitpilen 401 will work. We did not develop or test the Duke 390 link pipe on the Vitpilen. There are no plans to develop one for the Vitpilen at this time.”
Which is reasonable and not unexpected, but also not entirely helpful to my cause.
I bought an eBay cat/pre-muffler pipe that was described as for the 390 and the 401. It mounted fine under the bike and made things look tidy, but the muffler bracket wouldn’t line up to the mounting point near the passenger peg (over 1″ off). I gave it a go without any cat or muffler, but it was obnoxiously loud. Decided to go with Werkes cat delete and Fresco Ultra Shorty. It’s a “you get what you pay for” thing with exhaust.