The only intakes that are guaranteed to run perfect are the simota ones. There perfectly tuned for the zm. +I got my sri for $50 from protephile (pm him) You can also get a cai which is very nice.
Other then that people have had good luck with the injen (although not everyone) but the gains are great. (too bad the cels there)
I also ran the ebay live on speed intake for a while, really nice power but a cel and too much lean surge made it useless for daily driving.
Most of the cais will give similar power its all down to the filter element to really differentiate them. I recommend the aem dryflow for us.
If you really want to do something good, you need to cut off the air box then slap on a pod filter and make custom ram ducting, the car seems to really respond well to ambient air.
