Update to my PECOS mods. After playing around with my setup for a few years here is what I have:
1. nomex tape around both cooking lid and firebox lid (this stuff works amazing, make sure you clean surface and follow up with alcohol wipe down where you will put tape and let dry before adding the nomex tape)
2. tuning plates, spaced out more and more the further they are from the firebox (this helped keep temp more constistent from left to right, originally the temp was around 50 degrees off, now it's usually under 20 degress off)
3. removed all grates from fire box. - this is a deal breaker for me. i have now learned to keep the temp and coals hot in my large firebox, I build a large fire first and let it go for an hour and get A LOT OF COALS as a bed before I add my smoking wood. you can use lump coal if desired instead, but using wood works great too and letting it burn down. For me, the grates get in the way of managing the fire and moving the coals around. Without the grate in the firebox, now it's easier for me to manipulate the coals and wood closer or further from the cooking chamber to manage temps, before this was hard to do because the coals would fall down the grate or the grate was in my way. I got this idea after reading aaron franklins book where he had a picture of his wood stacked in the firebox without any grates, ever since my smokes are way more consistent and easier to manage
Good luck with your pecos!