Couple questions to start.
First, was this an issue before you did a full tune up? Next, does it move if you put in reverse or low gear range?
Last, when you pull the oil cap off and it is sucking air then that points to a restriction or issue in the PCV so let's start with this. Also, we are going to have to check for a vacuum leak.
https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge
I suspect you have two issues but we need to start with this info and go from there. Thanks
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Thursday, May 20th, 2021 AT 6:27 PM