Upgrade V4R4 to V5R1 - Performance Problems

Approximately 1 1/2 months ago, we made several changes to our AS/400,
knowing multiple changes was a risky thing to do.

Changes:

Moved from a 730 to 820
Upgraded from V4R4 to V5R1
Switched to EMC external DASD

One problem we are focusing on with IBM is 'open queries' do not seem to be
performing properly.  One job that used to take 30 minutes is taking 4-5
hours.
When the record is on the file, but the open query does not select that
record, it seems to run forever.

I'm guessing we may have other performance issues, but not at the above
magnitude.

Another problem, is restores seem to take longer on the new AS/400.

Has anyone else experienced similarly problems?

Thank you,
Michele