WHAT TO DO TO FIX PO300 CODE

My 1999 jimmy is giving a po 300 code it runs very rough. Has new cap and rotor, the plugs and wires are less than a year old. Used a cigar to blow smoke into intake to check for vacuum leak found none. Freeze frame data showed stft bank one 13.5%ltft bank one 0% stft bank 2 12.8% ltft bank 2 0% what would my next option be and how would I go about it thanks for response gary