Are you running any type of spacers? One of the best ways to find a vacuum leak is with a squirt bottle full of water. Spray it all over the intake and base of the carbs. As it sucks in some water the rpms will drop.
If the TR has a large plenium it will kill some signal to the carbs and when the secondaries open you get more air and not more fuel causing a bog, this is where a 4 hole spacer comes into play, by adding length to the venturies it will help to pull more fuel.