The inline T's on the muffler and supply side of the tanks allows for a fuel tubing coming out of the cowell. One is for filling the tank and the other (on the muffler side) is for overflow so you know the tank is full. You plug both before starting. Otherwise you have to use a third tank line which I think can be more of a source problems than the T connections. In 20+ years of flying I have never had problems with the T connectors.
I use Futaba FAASTso I can't use the Tacometer - thanks for specifying.