here is the Wiki info on the subject of flutter etc - it describes compressor stall where pressure escapes past the turbine and also the wear on the turbo itself - MAF (or equivalent) an a relation to over fueling is not mentioned - in my previous post I had omitted the bit about the throttle body and just mentioned revs dropping when clutch was dipped when changing gear )also assuming that a drive by wire throttle and flat foot shifting is not a consideration
There is confusion in the automotive world about so called "wastegate chatter" or "turbo flutter". A noise created on lifting off the throttle in a turbocharged car, commonly described as a chipmunk or a rattlesnake, is often stated incorrectly as being a result of the turbo's wastegate closing.
The noise is in fact the air compressed by the turbo passing back through the compressor wheel of the turbo after the airflow is abruptly halted by the throttle plate closing, called compressor surge. However, in some cases, i.e. where the blowoff valve/recirculation valve does not open fast enough or is set up to only react to high boost, some chatter will remain. Surge can occur on diesels when the turbo is attempting to pressurize the air at a higher pressure ratio than the compressor wheel can flow at a given speed. Most Diesel engines have no use for a blowoff valve as they do not have a throttle plate. The chatter noise is very noticeable on World Rally Cars, where anti-lag is used.
A compressor stall like this can cause excess stress and wear on the turbo's shaft or bearings under higher load applications of the turbo (around 15 pounds per square inch (1 bar) and greater depending on the trim and flow rate of the compressor side).
Actual wastegate flutter occurs instead under partial boost conditions such as partial throttle near the boost threshold. It sounds like FftFftFftFft not ShuShuShushu and is caused by the rapid opening and closing of the wastegate at boost levels near the spring pressure. It is commonly heard more clearly and may be more prominent on cars with modified intake silencers, up-pipes, downpipes, or an oversized wastegate incorrectly matched to that specific engine. Also, vehicles using on/off solenoids to control boost can do this under certain conditions. It is not harmful to the engine. Some may claim that it can damage the wastegate, which may be possible under some circumstances, however some vehicles flutter regularly inherently from the factory without any consequence.