Howdy New to smoking and just picked up my first BBQ - An Oklahoma Joe Longhorn. From all the good avice on this forum, I've already made a few mods. Got the right angle tubing from Lowes to extend the smoke stack down further: I built a diffuser plate for better heat distribution across the cooking chamber from the fire box. 18x24 16 gauge steel with bends at 2" and 9.5". Holes along the way small to big. Lastly I built a charcoal box from expanded metal: What has me concerned now is the drastic temp difference from the top of the smoker to the cooking grate. The installed thermo towards the top reads as much as 100 degrees difference from what I'm seeing at the cooking grate. I'm measuring the cooking grate with an electric thermo and have verified the top with the same just to make sure the cheap thermo included with the smoker isn't way off. As an example, if the cooking grate is at 250 (kinda where I want it), the top of the smoker reads about 350-400. I would expect the heat to rise, and the top to be hotter, but this seems like to much of a difference and I was hoping the above mods would have evened things out more. The cooking zone is basically still a cold spot even with the mods. Any thoughts or advice? I noticed the cooking chamber door is leaking quite a bit and am going to go to work on fixing that now. Could the leaks on the top part of the door be pulling the heat up and causing what I'm seeing? Also, the diffuser plate doesn't sit exactly flush with the fire box wall. Has a couple spots with very small cracks. Could that much heat be getting out and up there? That would be easy to seal. Wanting to get everything nice and even so I can start cranking out some delicious meats. Thanks in advance! Kevin.