Our house was remodeled before we moved in and the former owners moved the kitchen farther away from the main drain line under the house. Now there is not much of an angle from the kitchen to the main line. I seems like air pockets get in the line and keeps the drain from running. Any suggestions?

A 1/4' per foot slope on a horizontal drain line is adequate. That's 1" drop for every 4' of pipe. You don't get air pockets in drain lines. Sounds like you have a partial blockage in the line. Snake the line to clear it.

If there isn't sufficient slope to main drain pipe it will tend to clog up. Do you know if the previous owner did the changes with a building permit? You can check with the building department to see what they thought they were doing. Maybe even see if they had a plumber do the work, he could be called to recheck his work. Without the [ropewr equipment its hard for you to check slope. Call 3 plumbers to get estimates to see what they prropose, then you can decide if its something you think you can do.