Does anyone know the steps to get this grill to hold temp at 350 - 375? I have absolutely no issue getting it to hold temp at 225 - 250 for 15 hours at a time. But every time I try to hold at 350 for a few hours it shoots up to 400 - 425. This is a pic I took when I bought it, I've used it a lot since then for grilling wings to 15 hour packer briskets.