I think I would have insisted the dealer at least look in to the oil consumption, or did a leakdown test on your own. If the engine was burning the oil on accel, the oil will cause detonation, and the knock sensor will pull out timing and power. While 1 qt in 3k mi may not warrant a problem in a dealers warranty schedule, it certainly is higher than normal with todays engines. If that failed, I would have tried to get the ECM reflashed; it may not have the right program, or it may be contaminated. The ECM's in these cars do not allow full engine power in the lower gears to limit wheelspin and to protect the drivetrain, (even with the traction control off) and the program may not be ramping the power back up in the higher gears. That's why stock cars nose over on the shifts; it's not a trans issue; the ECM is taking fuel and timing out to protect the trans. The tuner boxes bring the power back with more aggressive timing/fuel curves in the lower gears, and firm up the shifts. I guess it doesn't matter to you now, since the car has been sold; I guess we're just trying to help the next guy who has the issue.