2017 Subaru Forester bucks in lower gears

What is causing my car to buck in lower gears of acceleration. 2.5 cvt Subaru says nothing showed on computer check. Got letter of possible issue for the and should be inspected.
Also occasionally smell of gas, NOT at fill or empty.

If the letter is from Subaru, have that issue addressed, then go from there.

With a CVT there are no “lower gears”. The whole idea behind the CVT is that there’s no shifting. Given the smell of fuel, this might be engine related.

If I understand the sensation you are feeling, it is often called “Rubber banding.” Rubber banding in a drivetrain occurs when the engine is “lugging.” Meaning operating at a very low torque point with very little power being asked for frm the driver. My Forester has the sensation too, particularly when I am rolling and applying just the slightest throttle in heavey stop and go traffic. It is one of the downsides of that particular drivetrain. I may be mistaken and you may have a different problem. If so, good advice above. Have it checked out.