Oscar lost 1:40 to Floyd in the first ITT (won by Gonchar). But on Stage 11 to Pla-de-Beret won by Menchov over Floyd and Levi, he bonked and lost 24.26. The following day he lost another four minutes. I can't find details, but perhaps he was sick. The only thing I can find is after Stage 13 he said "I feel strong now".
On that stage, two days later in searing heat he attacked 200km from the finish on a sawblade stage with five category 4 climbs, with a very strong group: Voight, Chavanel, Quinziato and Grivko. They finished 29:57 ahead of the peloton.
When the stage was over, Periero had a very slim 1:29 lead on Floyd, which he almost held until the very end through some very tough stages.
As I said, the guy wasn't a nobody. Not even close. He was 10th the previous year (behind Lance, Basso, Ullrich, Mancebo and Vino, all of whom weren't here). And he won a mountain stage, and just behind Landis - and could have won another had George Hincapie not wheelsucked him the entire time.
As I said before, the 2006 Tour was won on the road. Whether you believe that means Pereiro, or Landis was the true winner, that's up to you.