It's easy enough to tell whether you have extractors or not.
Pop the bonnet and look for something like these:
Extractors (thanks to whoever's car/pic that is)
As Eug said, the primary and secondary pipe sizes play a role in the power gain (plus where in the rev range it comes in) for the same reason as mentioned above with the volumetric vacuum.
If you're unsure, but still ready to upgrade, then your best bet is probably to take it down to a recommended local exhaust shop, have them stick it up in a hoist and then tell you your options
MV Automatics is definately what I meant, it's on my list of things to do with my 34.
Other than that, you're best off searching in this section for all the usual NA mods to do.