you check your ebrake? Could be the first signs of a binding brake... How about rotors or the caliper pins... If the caliper pins were beginning to seize, then you'd get the squeeking (more when they're hot after braking)... Under load (acceleration) there are more torsional forces in the rear that if they were beginning to bind would cause the squeeking you're experiencing.... Rotors could be warpage, but that wouldn't come and go typically.....
DCT Electronic Shifter
Bilstein and H&R sports suspension, Rogue Enginerring Race Brace
AA Stage2 tuning
Conforti CF Cold Air Intake
Hamann Front Spoiler and Side Skirts
BMW OEM rear wing spoiler.
M3 SMG Paddle Steering Wheel and M3 Seats
18" M6 custom painted wheels
Custom red kevlar interior
VIS CF Hood