My gas dryer doesn't seem to want to dry clothes anymore, if we open the dryer it is getting the clothes "warm/hot" but not "hot/hot" so we have to run the cycle several times before they will dry. I tried putting it on timed dry instead of sensor dry and it made no difference, they still aren't drying.

I have cleaned out the lint trap and run the diagnostic test "T10" and it came back "HI" so I am guessing its not that. I can see the flame kicking on but I really don't know where to start doing any other troubleshooting. What do I look for to identify the bad part? What test or tests can I do/run to narrow it down?