Keep getting p0172 code on longer trips on 1998 GMC Sonoma

I have changed the o2 sensor and the tps that was acting up but I still get the code on longer trips. I have clean the throttle body with spray and don't believe there is a MAF sensor on this motor. The truck runs great but the fuel economy is lower than it should be. Starting to scratch my head!

Asked by for the 1998 GMC Sonoma