Steve,
The injector I got from Glenn is plumbed-in at the outlet side of my burner. It's not adjustable, but draws so much better than the others I have tried. It also lasts a long time using high-alkaline solutions.
With the 1.8, I find I am drawing 2 to 2 1/2 times more than the injector that came with the rig or the aftermarket injectors I had been buying. I hadn't realize that injectors came in different sizes, but am glad that Glenn educated me!
Most jobs, I am running 200' of hose and sometimes use a 24' extension and never have a problem drawing chem.