A map width enhancement groove is a pathway between the front of a compressor cover and a slot on the inside of the bore, well behind the leading edge of the compressor wheel. A map width enhancement groove is and was designed to prevent compressor surge period. The Patented Tunable race cover we offer allows that groove to be adjusted to suit a particular engines VE, there is no cheating power gain on our design, but simply a way to keep an application out of surge and a way to move power from the front of an engines power band to the rear. A map width enhancement groove is to prevent surge and they come standard between 200 and 250 thousands, if you have an engine that the VE is on left field on and the turbo surges, adjusting the map width groove allows you to take it out of surge therefore making say a 6 cylinder and a 440 ci engine perform similar. On a single 76mm with a 3rd party testing they were able to also move 45 or 50 hp from the front of the power band to the rear, so this is a nice tuning option as some engines have lousy bottom end and need more power to get moving, some have way too much low end and we can see the benefit of moving that power to the top end where traction is better.