grasshopper, morning.... ECA, or encapsulated citric acid, will add a tartness to the meat... Fresh cracked black pepper adds a nice spicy flavor.... cayenne pepper, Thai pepper, hot Chinese dry mustard, five spice, white pepper, ginger root grated.... Maybe some Chinese hot sauce to keep with the teriyaki theme... Doing a fry test of the sausage, before stuffing, will give a "fair"assessment of the final flavor.... ECA will not come through properly.... It needs to be cooked above 135 and left to bloom for awhile and permeate through the meat... I think everyone tinkers with recipes when it comes to making sausage... You can find good mixes but none are perfect... Write down everything you add and the quantities in the event you want to duplicate the recipe.... I use a grams scale to weigh stuff... It is more accurate and reproduce able...
Try some fresh spices... grind them yourself.... big difference... Dave