Thanks for all the info. We have been doing alot of testing.
We had set the following parameters:
optimizer_index_caching=99
optimizer_index_cost_adj=10

and updated the stats.

If I use rbo (rule) and set the parameter optimizer_features_enable=8.1.7, the report runs in 16 seconds, if I use cbo (first_rows or all_rows), I gave up after 10 mins. Also if I use RULE and set the optimizer_feature_enable=9.2.0, it is still running after 10 minutes.

Thanks.