I have been having some issues with the car wanting to buck or surge and it seems to be tied to accelerator pedal position. I am currently running a 5star 91 octane tune and if I put the car in sport mode and put in first gear around 2000 to 2500 rpms the car will begin to buck and the TAC percentage jumps all over the place from 100 to 28 to 74 to 63 and so on. If I floor it then it seems to hold 100%. It will also buck under normal driving with moderate acceleration. Not sure what to make of it. I tried to put the car back to stock tune and it wont run right, just stumbles and misfires and several messages come up like backup sensor failure and advancetrac failure? Put car back to 91 tune and now runs okay but still has bucking issue. Any thoughts?