Most MAF sensors are only good for about twice there rated application. Thus in a Skyline it comes with 270hp thus the single MAF is good for around 500hp. But since a single Turbo 300ZX can produce more than 500hp you need to be able to still read the air intake and therefore they use two of them to split the air load and then the voltages get added together and sent to the ECU for processing. Kind of in the same way many of us are using Twin MAFS and an AFC to add the voltages together.
And the intercooler piping was coming from the lower right side and is being fed into the intercooler.