Stz1214

Hi everyone. New member here. Looking to get some advice. I have a 2007 C6 Corvette Convertible Base model. No mods except a Borla ATAK Exhaust and Halltech air intake. Been having some issues lately with the service charging system notification. When driving the car, if i reach 3500 to 4000 rpms, the voltage drops significantly from its normal 14+ volts down to the 10 -11v range and the service charge notification appears. When the rpms drop back down to normal cruise levels the voltage stabilizes and returns to its usual 14+ volts. Took it into the shop to have it looked at, replaced it with a brand new factory unit alternator. (GM/AC Delco Original), however, service charge notifcation comes on and stays on after startup and does not go away. Figured alternator might be defective sent away for a new one. Meanwhile decided to have the original alternator rebuilt. Put it back in the car, and same problem surfaces. Low voltages at high rpms. Not sure what to do at this point, put new belt tensioner on it, new belts. All wirings, fuses and grounds look good. Not sure what to do at this point. Anyone deal with this before? Any advice or guidance would be very welcome. Thank you in advance.