The gas flow is very low to the 3 bur...

Hi - assuming there is no severe kink in your gas hose and there isn't any other obstruction in your gas line, a likely cause is that your regulator is faulty and may need to be replaced. I don't think they are very expensive.

You may want to post your problem on the Jenn-Air section of this forum: http://www.bbqsource-forums.com

I've had good luck getting help there with my grills.

Pat