Your Surging idle may be from your EGR block....Has this problem been happening since you did that mod?? Ive heard more than a few people having problems blocking off the EGR.
It does nothing for performance but no one (including me ) wants that nasty exhaust gas recirculating through their system, So i know why you did it. You might try removing the mod temporarily to see if your erratic idle goes away.
Maybe and Maybe not....
