OK, so I tested things out and I made a mistake by sizing the pump at the same flow rate as the canister filter. Mazzei's website states that the pressure difference needs to be at least 20%. So I returned the pump and replaced it for one that will do 600gph to hopefully create the difference in pressure. Now the other question I have, if the booster pump is doing 600gph and the filter is doing 200gph, would I place the intake for the booster pump on the outlet of the canister filter (like my diagram on the previous page) or on the intake of the canister filter? I guess I can test both options, keep the outlet flows separate, and see which method keeps the flow to both pumps stable.

Also the other mistake I made was that I put the injector right below the lillie pipe. Maybe I need to put it right after the pump like on Mazzei's diagram,

Mazzei Injector Corp. - Selecting an Injector