InterBase 6.1 verses 4.1

Hello,

I'm having trouble with InterBase 6.1. For example, the following code runs
on InterBase 4.1 in 17 seconds, and with InterBase 6.1 it takes 7 minutes.
Is there something that I need to do. I'm also having problems with "like"
statements that ran before in 12 seconds and are now taking almost 3
minutes. Nothing was changed except the conversion to the new InterBase 6.1.
Is there some options or dialects that need to be set or something else I
should be doing. Is there a way to get back to InterBase 4.1?

Their after me,
Randy