If your soil nutrients are out of balance it is going to affect flavor and texture. Yellow shoulder, puffiness etc are nutrient disorders and flavor suffers.
http://www.oardc.ohio-state.edu/toma...olor.htm#color disorders of tomato.
About the only "additive" I know of to enhance favor is sodium (table salt-sea water). There have been studies with flooding fields with dilute seawater to boost flavor and anti oxidants. Sodium buildup in soil is bad for plant growth, but in areas with decent rainfall the sodium washes out each year.
http://www.njfarmfresh.rutgers.edu/d...toSalt2009.pdf
http://www.growingformarket.com/arti...-tomato-flavor
http://www.sciencedaily.com/releases...0428092116.htm