JDM Hachi has given you the term I couldn't think of, 'compressor surge' thats a better and more accurate term than the only one I could think of at the time (reversion) but the same problem is called both things.
When I was getting compressor surge it was recommended to me that an external gate would have solved the problem (just porting my internal gate was enough, so an external gate would have fixed my problem for sure). I would have loved to fit an external gate, but $$$$ were not there.
Hope you get it sorted MR.2 because compressor surge robs you power (or at least indicates there is more waiting to be unleashed with improved flow!!), get it sorted and you will be very happy.