Welcome to CDRLabs, b555!
I am somewhat confused what you are asking. Is your problem that you can only read at 40x or that you can only write at 40x?
If you can only read at 40x, try updating the firmware. I think that early versions of the firmware for this drive limited the reading speed to 40x for CD-R media, but this was fixed in later releases.
If you can only write at 40x, you will need different media. If you live in the US, Fuji media is a good choice.
I hope this helped!