I will take a look at it later tonight. But the first thing you need to do is add this to the top of your Scheme file: (declare (block) (standard-bin

I will take a look at it later tonight. But the first thing you need to do is add this to the top of your Scheme file: (declare (block) (standard-bindings) (extended-bindings)) These are statements to let the compiler optimize things, losing some dynamicism. That should increase it a lot. When it comes to tight loops, Gambit doesn't usually do as good of a job because of its garbage collector (it doesn't optimize for lots of small short-lived objects), which is planned to be fixed in the future.