2001 Chevrolet Performance Upgrades?

Hi all, I own a 2001 Chevrolet Lumina Sedan, and I love this car to pieces, but like everyone, we all want to squeeze every last bit of performance out of our cars. I havn't really found much on the internet to give my car more torque, or more horses, but I would like some ideas of what I could do to it, to just maybe get a little more out of it, without hurting it at all or voiding any warrenty's. I also do not want to spend a fortune as it already is powerful enough. And just FYI, I already have a K&N air filter installed. Any other add-ons like that, that any one knows of? Thank you.

Look more for the Monte Carlo. There's a billion things you can do to it, and the mc is just a two door lumina as far as I'm concerned :P

yes, I also just think the monti is a 2 door lumina. Good thinking on looking for upgrades for the MC, but is the MC a 3.4 DOHC, or is it the same 3.1, or 3100 as whats in my car? Would most 3.4 upgrades work on my car? Thanks.