Just before one of my injectors went, mine made a rasping noise that would clear and throw a load of black smoke out the back if you reved it.
I didnt know any better back then and had put it down to a faulty synergy tuning box.....all was well until the thing broke down on the way to wales. The aa diagnosed remote fuel pump so someone brough me one out but that didn't cure it so i got trailered back home and leak back test showed a knackered injector....now I always have 2 spare injectors stowed in the cubby hole.
A recording of yours would help someone on here point to if you have a problem