Alex,
You didn't answer my question.
It should be ok to use BackupPC_backupDelete as Michael suggested, even without taking a new full backup. I recommend using the -r option, which will re-run BackupPC_refCountUpdate:
su backuppcUser
BackupPC_backupDelete -h HOST -n 134 -r
It will merge changes into the prior backup #133 so that viewing #133 will look the same. But it should remove references to the additional files since they are not present in #133 (if people want to know the details, #133 has delete attributes for the new top-level directories in 134, so the merging will not copy them). After two nights of BackupPC_nightly runs the extra pool files should be removed.
BackupPC_backupDelete also supports the option of deleting just a portion (ie: a list of directories) of a backup rather than the whole backup. That should also have the desired effect - the files shouldn't be merged into the prior #133 since they weren't present in #133.
Craig