Adding more TempDB files will help with SGAM and PFS page contention. I would start with this post[/url] to make sure that you are not seeing contention during the operation.

I would also gather some additional information (latency) on the tempdb files using sys.dm_io_virtual_file_stats. Also gather some perfmon counters (Physical Disk:Avg. Disk sec/read, Physical Disk: Avg. Disk sec/Write) just to have some data for Dell when you call them. Do you still have the old system (where you didn't have this issue)? If so run the operation over there too with the same counters and compare and share that with Dell.