Drove home for the weekend from college (133 mile drive) and everything was fine, parked the car outside overnight in the rain, came out in the morning to move it and when i reverse i heard this loud grinding noise, kind of like i ran over something and the car stalled. I got out and looked, nothing under me or anywear remotely near me. Started the car again and heard the same noise, and i felt awkward jerks from the car. I slowly moved it further and still felt these jerks, even in 1st gear. It feels like somethings gone wrong with my tranny. The only mods i have on the car are a helix uppipe and full turboback, all catless, and a accessport running either economy 91 or stage 2 93 (the past trip and week it had been on stg 2 93) and the only major problem ive had was over a year ago when my car overboosted while on a manual boost controller and my factory precat got fried, i replaced both the turbo and the entire exhaust fixing that problem but that was awhile ago, havent had any kind of engine problem since, and in terms of driving, i drive aggressive but i can honestly say i dont launch the car except on very rare occasions, last time i did it was approx. 3months ago and in other gears i never speedshift or ***** my tranny any other way. Ok so the first thing i did when i parked the car again was switch the base map of the ecu back to stock. I started the engine and scoped out the engine, nothign seemed wrong, idle was fine, hoses were all tight, i went around back and noticed my exhaust fumes were really really dense and white, thick enough that i could see it from my rear view which isnt normal and its 57degrees F outside, wet and foggy, high altitude. I hopped in and drove it more very slowly up and down my street to get a better description of the noise and i noticed about 20feet into it the jerking feeling started to go away and the car felt like normal so i stopped, turned around and went a little faster, car drove perfectly normal except when i let off the gas, then i heard this very odd noise it sounded like some piece of metal was spinning very fast and gradually slowed down to a stop. I went faster, put it in 2nd, hit about 20mph and the noise got even louder, u only hear it wheni let off the gas. When i hit 20 i could hear and kind of feel it in the shifter through vibrations spinning faster, then slow down eventually (about 5-10 seconds) and go away. I parked the car back in the garage, the smoke problem is gone, no more dense fumes but im letting it idle there for another 15min so i can check for leaks or anything. Does anyone have ANY idea what could go wrong? im reluctant to drive itany further but if someone thinks its worth it ill take it out again and record it so u can hear the noise.
-OJ

Edit: Checked the fluids, no leaks.