Bought truck, was sitting for some time(9 years)... found it had failed cams and timing chains. Pulled engine and rebuilt top to bottom. Now... Engine running rich. Stumbles, loss of power and horrible fuel economy. Throwing the P0172 code.

Injectors, coils, fuel pump, IAC valve, TPS, coolant temp sensor, all 4 02 sensors, cats etc. all replaced. Has high fuel pressure; (spec is 49 +/-2) at 60 PSI and needle bounces around. Replaced fuel pump twice thinking the regulator was failed. Tried to buy the OEM fuel pump but it is discontinued, so bought the Delphi brand. Any help would be nice. Thanks.

 

Does it run any better once it warms up? Can you have a look at your fuel trims?

What brand O2 sensors?

 

Hopefully you put OEM 02 sensors in.It applies to all sensors since these trucks hate aftermarket off brands.
Also ,has the fuel pressure reading stabilized after thr new pump?

 

Try unplugging the o2 sensors and see if the truck runs better without them. If it does then you know the brand you got is no good.