thanks Dapi,

1) Are my critical business activities (queries & changes) executed with a appropriate speed? If not, why not?
YES, AFTER THE CHANGE I MADE BY ADDING "Optimizer_index_cost_adj = 10", THE MAP IS NOW RUNNING MUCH FASTER THAN BEFORE.

2) How is my server standing up to this?
SERVER IS FINE, I DID TRACE THE SERVER CPU AND MEMORY, IT NEVER EXCEED 50% OF THE TOTAL PHYSICAL RESOURCES THAT WERE AVAILABLE.

As I mention it before, one of my query did a FTS and I guess Oracle pick whatever plan with lower cost and ignore the index, now after making the change, the cost to execute the same query is higher but it did pick up INDEX and the app perform much better, but I run STATPACK again and CPU was still at 80% and DB SEQUENTIAL READ still somewhere at 16% and I don't undertand this.

statspack was run in about 20 min timeframe, with a few users in there.