I'd suggest you add a 3" exhaust down pipe, ported exhaust manifolds, and a high flow catalytic convertor in there.
Also, a big + with all the mods Pat listed, as well as what I have listed, is a custom PCM. Most people here have gone with Intense because they have been a active vendor, gearheads, and with a LOT of good input for the members here on BC as well as having the 2 fastest Bonneville'* in North America.
I myself have a ZZP pcm for the time being and intend on purchasing an Intense Custom Tune PCM in the spring when I have most of my modding done to my 1999 SSEi... I would suggest being you have a 2000 SSEi that you go with Intense as they have spent hundreds of hrs tuning BADSSEi and 8-BALL ..... both 2000 SSEi'*.
Good luck and keep a close on the mod bug.... it can really get ahold of the wallet.