Heat soak refers to what happens to the intercooler, i.e when the intercooler cant cool the air enough any more because its aluminum fins are heat soaked with well heat.. typically happens at traffic lights where the car can take on a shitload of heat.
The CAI system can also take on this but typically refers to the SMIC.. thats why a FMIC is alot better as the air charge is cooled much more efficently. hence why I bought the screwball thing