You can configure a Performance so that it's pretty hard to tell, if you skip various options.
It is a Performance if:
- it has a P85 logo (early cars were delivered without, but can be retrofitted at no cost)
- it has a carbon fiber dash (optional)
- it has a carbon fiber spoiler (optional)
- it has the grey wheels (optional, and you can buy them separately so you can't really go by this)
- it has alacantra accents (or it's Signature)
- it has contrast piping and alacantra bolsters on the seats
I think that's the full list. I think the only sure-fire way to spot a Performance is to look for the contrast piping on the seats.