smoking on gas

[steveemait]

I crudely set up my 2 burner (side by side) gas bbq for smoking as follows:

I moved all the lava rocks to one side and placed water soaked wood chips in a foil wrap on top them and the other side I placed a tray of water .

Starting the bbq on one side on lowest setting, with the lid closed my temp soars to 300f very quickly. To get it down to 250f I have to wedge it open about 2 inches so I loose the smoke, what I settled for was to have it open about 1in with temp of 280f.

Any idea on how I can lower my temp? I also tried turning the gas down on the cylinder, but this didn’t seem to have any effect. The thermometer I am using is brand new and I mounted it myself slightly off centre (away from heat source) about 2 inches above grate.

Thanks in advance