Cedar Planked Salmon PBC

I still can't manage to get the correct startup temp on the PBC. My last chimney start up, I used 45 briquettes and the temperature was lower then 275. I had to crack the lid multiple times to keep the temperature up.
Today, I utilized the lighter fluid method and followed the directions to as specified. 15 minute burn time after putting fluid on the charcoal and lighting the lid. The first pictures is about 8 minutes in.
After 15 minutes, I put cedar planked salmon on the bbq grate and closed the lid. The temperature started in the 350 and sky rocket to near 400. I used the magnets to get the temperature down to the 350 range. After the Maverick and Thermopop read around 145 I pulled the salmon and let it rest.
I then put sausage on rebar and reset the maverick. The magnet was still on the PBC and it started to downpour. The temp settled around 306 and I pulled the magnet off. I pulled the sausage off the PBC around 170.
I love the PBC but wish I could start it up and maintain the temperature properly from the start. The lighter fluid method was easier, no chemical taste on the food after letting it burn off. Next time I am going to close the vent less then 1/4 prior to start up and put the lid on around 12 minutes. No pictures of sausage due to down pour!

The salmon tasted great. For the higher temps in the PBC I took it off in about 20 minutes. Higher Ground, I my vent might have been more then 1/4 open. I am going to close it to a quarter open and put the lid on around 12 minutes. Are you guys putting the rebar or grate on at 15 along with the meat or are you putting the lid on and let the temp settle prior to putting on the meat?

I left the rebar out on the salmon cook. I will leave them in next time I am using the grate. Thanks for the replies. I love cooking on the PBC, just trying to figure out the learning curve.