According to the Pontiac Car Distribution Bulletin, shown above, the GTA Notchback option was canceled effective 08/30/1988. The Pontiac Car Distribution Bulletin indicates that no further orders with the Notchback option would be accepted, as they would be removed, and that there will be no 1989 GTAs built as Notchbacks.

The picture, shown above, is a copy of an invoice, provided by GM, that shows an existence of a 1989 GTA with the Notchback option. Due to the condition of some of GM's records, the VIN was cut off from the invoice. Note the GTA Notchback option - on a 1989 GTA

According to Frankie's GTA Source Page website, we know that there was 1 - 1989 GTA built as Frankie reviewed some of GM's documentation and was able to gather some production figures for the 1987-1992 GTAs. The figures that Frankie has on his website only count domestic GTAs, and not exports.