As I understand it, all shared hosting plans are considered equal, as far as CPU resources and upstream/downstream bandwidth, differing only in storage space and monthly traffic allocations, but I have a feeling that this was a rhetorical question.
Have you lodged a support request regarding your problems? It is possible that your particular server is experiencing problems that have not as yet come to the attention of DreamHost.
Have you checked the load on your server? (Log into SSH and enter the uptime command).
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