A lean mixture can have dozens of reasons. Problems with the injectors (fouled, defective) are just one of the causes. Very common are blocked fuel filter, defective sensor and air leak (inlet and/or exhaust).
Less common problems include mechanical engine problems like damaged valves or less compression. Or uncommon, but not impossible, defective new spark plug.
I would first try to find out whether or not it's a fueling problem before searching for something that's not there.