Chevyz78

i recently got a 96 rs with a 3800 v6 auto and it has a noise that sounds to me like a dry bearing but oil pressure is gd and i can only hear it when idleing or when its shifting gears. When i drove the car home at 65 mph there was no noise at all but it seemed like it was lacking power when trying to accelerate. I dont know a whole lot about these new engines but i was thinking it could possibly be loose torque converter bolts or a cracked flywheel but i havent had time to check it out yet. If anyone could give me some possibilities of what it could be it would help me out narrowing it down before i spend money on a new engine that it may not need. Thanx