Yesterday I purchased the Carenado 350i and it turning out to be a BIG mistake. First, the throttle down when approaching to land stays pretty much at flight throttle level. Secondly, when I reach an altitude of 6400 feet the aircraft loses control and sways back and forth. Lastly when taking off the aircraft tends to go left, there are NO weather settings causing wind issues. Anyone experiencing similar issues and been able to resolve, can't find a manual for 350i. 

I have the P3D v.3xx version of the B 350i. I cannot answer your first question as I am not experiencing either one of those problems. Your last situation, in the realism section, try turning down both the P-factor and Torque sliders to zero setting. 

If you "PM" me your e-mail address I can send you via dropbox, Bill's mod (v. 1.0) he did that improved the flight characteristics of this a\c. You can look at the B350i mod v.1,0 topic for its description. 

As raymie pointed out, the left turning tendency is realistic. It's the BIG pilots job to counteract this moment. Haven't read about or experienced the other problems. 

I've been seeing a similar (I think) throttle issue lately with several aircraft with my Logitech 3D Pro stick in P3D.  Using the built in throttle doesn't always go to full throttle or all the way down to idle.  When I feel this is happening I just hit the F1 or F4 key to push it that extra bit in the right direction.  Wish it wasn't happening that way and calibration doesn't seem to fix it.  But it does work for me.