FYI, my P0171 was caused by the ISR vaccum line, that line directly controls how much fuel is sent to the injectors, mine was not getting enough for about ~6 years... randomly throw p171 cpdes, then be fine. After i did the 'Deck Plate' mod, the p171 was on all the time... removed ISR put the vac line on the tube i used and voila! though i only get about 16MPG now.... :decision: