Corruption Parameters Increase High Physical Read for one query

Hi Oracle Experts,
Here is what I am currently facing in my non-prod environment:
We are testing out corruption parameters in non-prod environment and doing a perf test for them and we found that one SELECT query has seen significant decreases in performance; What I mean by that is after adding corruption parameters query is executing 40 sec compare to 18 sec and less. Also, this query is widely use by user in Prod environment, so performance degradation will create serious impact on their work.
I have generated AWR Diff for baseline and perf test following are parameter we have set for corruption test:
db_block_checking (Baseline) LOW (Perftest) MEDIUM
db_block_checksum (Baseline) TRUE (Perftest) FULL
Load Profile from AWR Diff are below:
Load Profile
1st Per Sec 2nd Per Sec %Diff 1st Per Txn 2nd Per Txn %Diff
Redo size: 758,356.06 752,760.94 -0.74 67,161.76 66,631.71 -0.79
Logical reads: 104,637.62 108,677.76 3.86 9,266.95 9,619.77 3.81
Block changes: 1,578.11 1,560.15 -1.14 139.76 139.76 0.00
Physical reads: 103.78 544.41 424.58 9.19 48.19 424.37
Physical writes: 108.94 107.13 -1.66 9.65 9.48 -1.76
User calls: 3,477.02 3,497.26 0.58 307.93 309.57 0.53
Parses: 948.36 949.61 0.13 83.99 84.06 0.08
Hard parses: 0.79 0.54 -31.65 0.07 0.05 -28.57
Sorts: 121.48 120.32 -0.95 10.76 10.65 -1.02
Logons: 0.36 0.27 -25.00 0.03 0.02 -33.33
Executes: 1,575.55 1,591.40 1.01 139.53 140.87 0.96
Transactions: 11.29 11.30 0.09
If we gather stats for tables involved in the query than it performs well in fact with in 5 Sec, but I believe in prod we can't gather state very often.
Questions:
1) How to remedy this situation and have query perform well along with corruption parameters?
2) Does corruption parameters have impact on SELECT query too, I believe it will have impact on INSERT and UPDATE.
3) Any reference to Doc will be highly appreciated.

1) How to remedy this situation and have query perform well along with corruption parameters?Use faster CPU. Checksum is a thing that needs to be computed.
2) Does corruption parameters have impact on SELECT query too, I believe it will have impact on INSERT and UPDATE.According to docs corruption parameters do not have impact on SELECT queries.
However, I believe, checksum has to be recomputed after delayed block cleanout that may be done by SELECT query after big update. ( http://jonathanlewis.wordpress.com/2009/06/16/clean-it-up/ )
3) Any reference to Doc will be highly appreciated.
Why is it difficult for you to find the docs yourself?

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