I think he meant two to three layers of coil windings. Which might equate to more like what you're saying 40 to 50 turns.
Quoted from jrpinball:The pop bumpers on that game are not very high powered, but by design. They are in a tight nest, with stand up targets in close proximity. Additionally, they are ganged, with both green or yellow bumpers firing together.
Removing 2 1/2 to 3 turns on the coil will do absolutely nothing. More like 40 turns to have an effect, but I'd give the game a few dozen plays as designed before considering modifying it.