yamaha xs360 needs more steam!

Moin, I’m new here and I want to ask the experienced bikers what you can do to get more power out of my machine. It’s ́ne Yamaha Xs360, I shot them last year on an oldtimer market cheaply and it doesn ́t go away enough. At the dealer near me they told me that I should try it with new nozzles in the carburetor and a sock instead of air filter box. The bike is not registered so can be tuned to heart pleasure. If I should get nozzles, which one should I take, so how much should I increase? and d is there something I have to pay attention to? e.g.: output size of the nozzle 92 to 98 or how much??? I thank you already in advance and hope you don’t have any good advice. p.s. the machine now has 27ps