Merritt drew a Surge Monster - aka a GT-RS turbo for an RB26 , or any turbo that operates to the left of the surge line , a pair of GT-RS on a 2.6 liter engine surge excessively.
When the pressure ratio between the air inside a turbocharger and the atmosphere increases, but the flow rate through the turbocharger remains low, surge occurs. While the concept of surge is a rather complicated tasked to explain, it can be easily identified as a swishing noise. There are certain size turbochargers when mated to particular engines that are known producers of surge. A good example is the use of twin HKS GT-RS turbochargers on an RB26DETT engine. You can really hear the surge at low rpms. For this reason the GT-RS has earned the name surge monster.