When you fit any type of SRI you must clear the previous "learned" adaptive fuel strategy settings from the ECU. Did you disconnect the battery after installing the intake for 5 minutes or more? Most SRI instructions tell you to do this.
Once the new intake is fitted, let the car simply idle for a few minutes. If you are still having idling problems after a reasonable amount of driving time has elapsed, you have likely unintentionally introduced a vacuum leak into your intake system. Check the intake tube to throttle body connection clamp in particular and also where the MAF screws into the intake tube. Both areas must be air tight as they are behind/near the MAF sensor. Airflow after the MAF isn't compensated for by the ECU.
If the car ran fine before your modifications, don't go chasing other possible causes until you've rechecked your work.
Last edited by BC_ZX3; 09-27-2011 at 11:25 PM.