I had the same issue with my last gp. I was able to tune the problem out by increasing the duty cycle of tcc. Do you have access to a tuner? It has been a while since I have done it but I am sure someone else can chime in as to how much to adjust the table.
I had the same issue on my 99 GTP, ended up setting the MAX duty cycle table to 99%, and the MIN duty table to around 45% across the board. Keep in mind that doing this will make your TCC engagement very firm (almost feels like another shift when it engages).
2003 Grand Prix GTP.... the journey begins again....
E85 Self Tune with HPT, 80# Injectors, Gen V 3.4 pulley, SD Headers, AL605 Plugs