How can I identify and fix bottlenecks in an Oracle11gR2 import
Depending on the edition (enterprise, standard, express, etc.), the licensed options (particularly the Performance and Tuning Pack), and whether you have installed Statspack, I would start by taking an AWR or Statspack report for both system when they are executing a similar workload and compare them.  If you are licensed to use the AWR (note that querying the AWR tables violates your license agreement if you aren't), use an AWR report.  Otherwise, assuming you (or the prior DBA) installed Statspack, use that.  Otherwise, you'll have to install Statspack in both systems.

If your guess is correct, I/O is the bottleneck, and the problem is that the I/O subsystem on the new server is slower than the I/O subsystem on the old server, you would expect that the top wait events in the report on the new server would be primarily I/O, that the amount of I/O would be consistent across the reports, and that you'd see that individual I/O operations on the various tablespaces and data files were consistently slower on the new system.  Otherwise, comparing the reports should tell you what the bottleneck is (though an AWR report has a ton of information and a comprehensive discussion of interpreting an AWR report is a book not a forum post).