There seems to be some way of maintaining the faster speed for level 9, but I can't manage to do it consistently. I can do it fairly often in 9.1, but I've only gotten it once in 9.2. Any ideas?

3 years later, I have finally verified that you can maintain fast speed in 9.1 by flying forward to catch the 2 shields up top, then dropping INTO the terrain in the middle of the screen. Do NOT grab the extra life, as that will slow you back down. After you pass the extra life a bit, fly back to the upper portion of the screen, not the lower part. This should maintain the speed boost through the rest of the level. Still no idea how to do it on 9.2.