Not shounen Ai but yaoi:
Miscreants and Mayhem
Roses and Champagne
JINX
Aesthetics of Unpleasantness(he has the badass guy vibe in front of his partner)
PLACEBO(not that much mafia vibe)
Ogus's Law
Thirst(kinda)
I haven't picked up jinx yet but there is no way in hell you'd think he has a lovey dovey vibe to him
No it's not Jinx with the boxer-guy but love jinx a whole other story
Oh ok then
Can someone recommend me a shounen ai about a short, short tempered guy and a calm tall guy with a lovely dovey act in front of short dude but has a mafia leader vibe Infront of others