Tuning 2016 PX150 Euro 3 but retaining the catalyst


I'm new to Vespa tuning  but have owned a Vespa Douglas 150 Sportique, and an ET4 in the past.

I'm very close to purchasing an as-new 2016 PX 150 euro3 with catalyst.

I would like to have a little more performance than standard, but want to retain the catalyst, which I know is very restrictive.

Has anybody an experience of dong this, and can offer me any advice?

I  have found lots of information online, but everyone starts with 'change the standard exhaust'.

Would adding a larger cylinder kit and less restrictive ignition but retaining the standard exhaust offer any benefit?

Has anybody tried adding a standard or performance catalyst into a performance box exhaust, or does it just remove any benefit of the performance box?

Thank you