LIM leak? swaped 4 felpro set but mist coming from back of engine?

swapped LIM gasket set and used torque wrench, coolant bypass pipe was sealed with rtv due to not having the seal that goes into the water pump and the pipe coming out of the intake manifold. Didn't hav any leaks or problems for two weeks , then today got the mist again from the back of the engine area, cant see any leaks around the LIM area or either side ,water pump, coolant bypass pipes, etc. Car drives just fine and doesn't over heat. lastly heat works and system was bleed twice. any ideas

Pressure test the cooling system and try to locate the source, no other way.

wheres a good place to buy a pressure checker? online or in person?