Is 32 bit IDAPI slower than 16 bit IDAPI ?

We have created a 16 bit database application in Delphi 1.0
which scans .DB or .DBF tables with approximately 30000 records.
On each record is performed some operation.
After recompiling this application in Delphi 2.0, it runs 2.5 times
slower then 16 bit version. We have discovered that the offender
is DbiGetNextRecord function from IDAPI which 32 bit version is
3.5 times slower than 16 bit one.
We have tried to set maximum priority of IDAPI session thread
but the application ran only slightly faster.

Is there any way to solve this problem, e.g. by setting higher
priority of IDAPI ?