FS9 aircraft behavior in FSX

I have just changed to FSX, because I now have a computer who can manage it. I have been a long time user of FS9, but desided to give FSX a chance. I have used some time in tweaking FSX, and it's look all right know. Here are my questions:1. Why are my downloaded aircraft stopping their engines, when I select and load them? Some of them are easy to start with Ctrl+E, other aren't possible to start.2. I have downloaded and repainted some aircraft in FS9, and tweaked the aircrafts a little bit, so I was satisfied with their performance. That I mean is, they fly very well (my opinion) in FS9, but in FSX it feels like they be short of power. I have now tried 2 jet aircraft, and it feels like they have about 10% less power in FSX, compared with FS9. I have also tried one of my turboprops, and again they fly very well in FS9, but in FSX, it even haven't enough power to take off. If I look at the gauges, none of them come over 60% power. As I said, in FS9 it works fine, and power and torque settings works fine individual as well. Now my question: Do any have have/had the same problems , and do any have a solution?Best regardsHenrik