I have an 03.0 Sedan 5AT.

How can I check if i have the VLSD?

If it's performance package, then yes you should - if it's base model, then no (unless previous owner installed one later). If you are original owner you'll know if it's base or performance... otherwise you can tell by the wheels and suspension (unless they are now aftermarket).

Do you spin inside tire easily when you make spirited 90-degree turns? If yes, it's probably open diff.

Correction to my previous post - it was brought to my attention by a very reliable source (Mr. DaveO) that the 03 did not have VLSD as an option... so as long as no one installed and after market LSD you have open diff. (I'm 04.5 and tend to forget the pioneer car has some quirky things different).