After warms up about 20-35 MPH starts sputtering?

Hello,

It sounds like you might have a vacuum issue. Which includes the PVC.
First you need to check for vacuum leak.
You need to inspect the vacuum hoses for cracks or any type of deformities.
Many times a vacuum hose will crack at the joint. So pay close attention to those areas.
You can also test for vacuum leak by spraying carb cleaner into specific gaskets and joints. You will have to make sure the engine is running when you perform that test.
Here is a helpful video:

https://youtu.be/xN5pcM-5bso

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Looks for any damages around the PCV hose and connectors.

I have attached diagrams for your reference.

Please let me know of any questions.

Thank you.