We are having an issue with our toilet. It wants to clog whenever you go number 2. We've had the sewer from the house to the street snaked and it has good flow. The vent from the roof also has good flow. You can actually hear the water rush when the toilet is flushed. We also replaced the old toilet with a new 1.6 gallon flush. When the toilet is clogged, you can hear it gurgle and eventually the clog will go away on its own.

What can this possibly be?

Thanks

you can hear it gurgle you might think the vent is clear but the gurgle says otherwise. Go back and snake the bathroom lavatory roof vent. Put out enough snake to reach the base and 15 feet more. Let me know if that helps. Back to you, Tom