Note the name, insulator. What they do well is prevent heat soak. Your plenum gets super hot through the LIM. This means when weather is up and you give the car a bit of go for long periods, your tune is boned as the air temp sensor is in the airbox.
I can notice a decent difference in mine as the plenum only gets hand warm. My air temp sensor is by the throttle body due to the compressor. So in conjunction with other mods it aids response and economy. On its own, meh.
Arguably the longer runner makes more low down torque, but you'd need a sensitive bum to feel it.