Rob,

I know the end of the rope feeling so I thought I would at least try to help out. I'm assuming at this point you have double or triple checked that the same code is in place; have you also checked the db config and file config of the db in question? Have you checked the query plan on both environments to ensure they are identical? In addition I would also check the server config for RAM; MAXDOP etc. Confirm there is a difference after running DBCC FREEPROCCACHE as well; could be an old query plan in there.

Are either of the hard drives you’re running on different, SSD vs.15k vs. SATA? Are they on the same SAN, different SAN or local? Even if the hard drives are the same in the same mirrored configurations it may be that they are different SANS different caching.

Any other information would be helpful if you can provide it.