Any recipe depends on the quality and wholesomeness of the ingredients. But with sausage, good results depend on the process as well.
Of course, your smoking/cooking technique matters. But assuming you start with good stuff and don't booger up the cook, the primary root of success or failure is salt, fat, and grinding.
Salt precision counts. If you're making dinner, measuring spoons are fine. But when making sausage use a precision scale.
The ratio of meat to fat, and the ratio of salt to the combo of the meat and fat, are critical to how your sausage turns out.
Repeating (or improving) results depends on knowing exactly what you did the time before. Be as creative as you like with herbs and spices. Salt and fat require precision.
Another key factor is the grinding technique. Many tools and methods work, but all depend on the meat, and preferably the grinding equipment, being well-chilled as the meat is ground or chopped. Best is to stage both in the freezer and process the meat only when partially frozen. It's the difference between slicing and smearing the meat, which produces a dramatic difference on the plate.
Equipment should be clean and sterile. Wipe a little cooking oil or food-grade lube on the plate surface that faces the blade, and the inside surface of the stuffer.
This recipe calls for two grinding steps, some others call for just one. I prefer two, but it's a matter of taste. If I was in a hurry I wouldn't hesitate to grind just once with the finer plate.
The E in ECA stands for "encapsulated". That means the meat is protected from the ingredient, citric acid, by encapsulation (hydrogenated vegetable oil) — which forms a protective shell around citric acid. It melts and dissolves at the right temperature to expose the citric acid to the meat at the right time.
ECA works great if you follow the instructions, but if you subject it to excessive mixing the encapsulation will be damaged. And if you stage it in the fridge overnight the encapsulation will absorb too much moisture and start to dissolve. Either exposes the meat to the citric acid too soon.
This stuff is not fussy, but neither does it tolerate shoddy technique. Treat it right and it's spectacular. But get sloppy and you can ruin your batch.