Uh...you already found the problem.
You should have no change when you open the pcv to allow venting. By doing so you introduce a small vacuum leak, but you shouldn't have any pressure or any extreme pulling of vacuum.
Please check the pcv valve.
If you think the pcm forgot where TDC is and the timing is off because of that, you would want to perform a case learn (crankshaft variation learn), not a crank sensor replacement.
These would be the steps I'd take to further diagnose the issue. And I have seen a case learn change the way a car idles, runs etc. Usually it doesn't appear to make a difference, but there'* the exceptions.