I've had the car for 3 years, it always blows a puff of blue smoke on start up and burns 1 qt of oil every 800-1000 miles but in the past few weeks i've noticed some blue smoke in the rearview mirror. I had a buddy drive it and I followed and saw smoke when he let off the gas or changed gears. It runs smooth and has no noticeable loss of power. Is this a turbo issue or rings? Engine was rebuilt only a few thousand miles ago.