hey guys. just need some help please =P

ive got a couple problems with my VZ SV6 5 speed auto.

First of all. when ive got the car in tiptronic mode, and hold it in the gear till say 4000revs , and then lett off the accelerator, then engine makes like a knocking noise. its not always but it happens bout %90 percent of the time. Ive checked everywhere on the net and cannot find any solutions =[

Second of all, when i accelerate full throttle, it can vary from gear 2-3-4, and at random rev between 3000 and 6500, it wont accelerate any more.
its as if it has a rev limiter at that certain rev. To fix the problem i normally just let off a couple minutes and then it can return later at any time.

Lastly when i turn corners semi hard, from the front of the car it sounds as if something is sliding from one side to he other. My car has been lowered with SL all round if it helps.

hope u can help me out. cheers guys.