I have a Scion xA 06 I was driving to work one morning and the rpms dropped from 3K to 1K loss of power I could press the gas pedal and it would make the rpms go up and down, up and down, so I took it to the mech. he said it showed that the 2 cylinder wasnt working right so he replaced that coil pack,it worked for a day now it is doing this again but not all the time just out of the blue. oh and it sometime it idles really rough and the start idling fine.I really need help thanks Patrick

 

Did your mechanic show you a fault report, or did they just jump to replacing a part. Get your xA scanned with a decent scanner that can pull historic and sporadic faults. Let me know what you come up with.