I'm having the same issue on my mother in-laws bone stock 02 GPGT. Been having fuel system rich for about a year now.
Replaced the o2 last year with a coughboschcough and that didn't matter. I failed a few months later. Just replaced it am month ago. Her LTFT's are solid -12 at idle.
Map is at 32-33 at idle.
Already replaced the FPR a while ago.
Debating on if its the POS bosch o2 sensor and find a stock ac delco or a Denso to throw in there.
I also replaced the MAF sensor a few years ago as it was bad. Not sure if this thing just need a tune since I replaced the maf?
