I was down 6hp on my ABF from last month at another RR event there, and the only thing I've done since was new cold air intakes which should have seen a very slight improvement, oh and new plugs and oil...
I know 6hp is not much compared to you guys running boost and other fancy stuff, but my car has always been very consistent at JKM's rollers and out of 4 or 5 times I've been there I've always seen an improvement over the time before, except once when I knew what the problem was, so I do think the rollers were under reading on Saturday.