Pacific Gas and Electric Co. admitted only recently to federal investigators that the San Bruno gas pipeline that ruptured disastrously last year at a flawed seam weld suffered a leak at a similar weld 22 years earlier, the head of the agency leading the probe said Wednesday. PG&E's belated revelation...angered officials, who called it potentially critical to the investigation into the Sept. 9 disaster..., in which eight people were killed...National Transportation Safety Board...Chairwoman Deborah Hersman..., said..."We are very concerned about this late notice at this point in the investigation...We would have expected this to come out a long time ago..." ...PG&E has been forced to concede that its record-keeping is deficient after failing to meet a March 15 deadline for turning over all safety documents... [also includes comments by PG&E spokesman]