hi Yen,

just saw this thread. i had the same problem with my Sentra as yours after i had my headlights changed to XP sa Petron. I don't know if meron sila nagalaw or something, but the idle RPM dropped from 850 to 400 with A/C, 300 if walang load.

brought it to NGO- Libis, kinabitan lang ng Consult II, then dun in-adjust yung idle RPM back to 850. ayos na ulet.. la pang 10mins.

SA Remo ang nag-assist sa ken. Hope yours get fixed as well.

Cheers!