Dick,
I am sorry that I can not give you a simple answer to your question. The intake temperature will vary widely with the ambient temperature and boost pressure. Also, there is no maximum boost pressure for all Cat engines. However, there are maximum boost pressures that are programmed into the software, that operates the engine. All models of Cat engines operate at a different maximum boost pressure.
Most C12 engines will run about 24 PSI at WOT (wide open throttle) at 2100 RPMs, where as the C13 will run about 58 PSI under the same conditions.
CAC (charge air coolers) are sized to the original installation by two factors. First, it must offer virtually no restriction to the amount of airflow that the engine is expected to need. Second, the cooler must have enough surface area to dissipate the projected heat load. That is what engineers are paid to do. The problems arise when the engineers are restricted in physical size, by the design people that think that a particular product will look better with a smaller grill area, or by the accountants (bean counters) who demand a certain price point.
The guy sitting in the front office is expected to solve these conflicts, unfortunately, it does not always happen to the benefit of the product. Therefore, the new owner ends up with a product that underperforms expectations.
Gerald