I will do my best to remain unbiased in this reply. I can give no valuable information to the SRP liq/air plenum, as I have no specs or ever used one. I can however give some very useful information to consider. Our Billet ULTRA plenums (liq/air) have gone through some very rigorous R&D testing and improvements over the years. There is not a straight forward answer as to temperature drops at given boost levels as the temps will change the longer you stay in the boost. If others are using dyno data for comparison then that is easy, on a high hp turbo, making 30 psi of boost, pre-intercooler temps are over 300 degrees F (150c) after the intercooler we see 100 degrees F (38c), this is with our previous core. We now have a new core and plenum design and the temps have shown to be 40 degrees F. lower yet, and these temps are while using our circulation systems, with a water pump and a heat exchanger, temperature drops are more significant when using ice water.
Now keep in mind, I would not recommend anyone to rely on dyno #s alone, as a dyno run only lasts 5-6 seconds. In real world use you will not see steady temps, the longer you remain in boost, the higher the intake temps will climb, and you have the heat transfer process which puts heat into your cooling medium, which also raises your intake temps, in land speed use, which is the most extreme due to the rider running wide open throttle over the course of 1 mile or more our ULTRA plenums have maintained intake temps of 150F (65c) while running over 30 psi with pre-intercooler temps approaching 400f.
When we make claims with our products, such as 380hp on pump fuel, this is not because we have tested them to 380hp on pump fuel, its because we have tested them to the point of failure on pump fuel, then adjusted the rating by a specific percentage to give the customer a margin of safety. Also keep in mind that the circulation system will also affect your intake temps, water flow is important, as is how the coolant is circulated, an individual could take one of our ULTRA plenums, and install their own water pump and circulation systems, and get very poor results, all the components have to work together efficiently to get good results. I hope this maybe clears up some of the questions asked.
Richard