Modern Vespa

2003 px125 with a polini 180 kit and scorpion exhaust. This is the set up someone I know is running they currently have a 20/20 si carb and are looking to try and find a bit more speed. The advice they were given was to use a 30mm dellorto a rubber mounting and to lose the air filter.
What would this achieve realistically and is it ok to run without a filter? Any advice appreciated.

I would think a 30 mm phbh is way too big for that setup. Unless of course you've done some fancy porting, adding a reed valve setup etc.

If that's a bolt on polini 177 without any extra porting and just the regular rotary valve, you'll probably be fine with just an si24/24.

A phbh 26 or 28mm might add a little extra at the top, but you'll loose quite a bit of low end power.

No air filter means that your rotary valve won't last long.

Anything getting in there is going to "sandpaper" it down until it fails.

A porting and crank job would be the next logical step.