Foley acknowledges the IM's are real. Yes, ginned up IM's will soon float around the Net (and I expect to see some on FR that will inevitably have me laughing) but I'm sure the people involved can tell the real thing from the hoaxes.
Foley admits he sent e-mails. There has been no admission about the IMs. Further, it is doubtful that he would recognize what was written in an IM from 3 years past. He may remember sending bad ones, and then when presented with what has been pushed by the media, cave without actually being sure those are the ones he sent.