Just got the motor up and running again but every so often while idling the motor will surge back and forth from 1k to 2k. Sometimes there is no surge but it’s becoming more consistant. Could this be a vacuum leak, or could it because I’m running with no second o2 sensor on my swap? It happened before I took the motor out too but now I’m getting pretty sick of it since people think I’m revvin on them all the time. Any ideas would be appreciated.