There are thousands documented varieties of tomatoes out there, some more acidic tasting than others, some balanced with sweetness and acidity, some more on acidic side. Some purposely crossed, some developed for whatever reason by whomever...
Heirlooms do offer some of the most diverse array of flavors. Personally, pure acidic varieties don't agree with my taste buds, but from what I've grown in the past, if you want a zing:
Pink Berkeley Tie-Dye
Rutgers (mostly acidic, no sweetness at all to my taste)
Few others noted for their mostly acidic flavor is Purple Calabash and Wisconsin 55...
Good luck, hope you will grow something with the taste you are after!