Andre: the problem is well known. Many older FS9 aircraft were made with techniques that are no longer compatible with FSX - the textures need to be recompiled.
With SP2 the situation has got worse. Some payware aircraft that were ported into FSX-SP1 now have texture problems in SP2. These problems have been discussed in this forum several times.
Unless the maker is prepared to supply a patch with recompiled textures then the only way is to do it yourself.
FSInsider gives you the pointers how to do it, but it is a way beyond my skills, so I have just deleted the aircraft and continue to enjoy those that have transferred satisfactorily. We have dozens, but end up only ever flying a few so its good discipline.
All I would hope is that retailers tell us if the plane is compatible with SP2, or that a patch is available.