I had the same problem with my 13 RTS SE5. I swapped the O2 sensors to see if it changed to P1174 (good idea suggested by NancysToy). Since there was no change, it was not the O2 sensors. I then installed BajaRon's plugs and wires (excellent). But I still had transient P1175 codes. Since removing the canister (thus taking the purge valve out of the picture) no more codes.