power loss 2000 Silverado poor on mpg and lacking power

[Mace]

Having a major loss of power especially noticable when going up hill, and terrible fuel mileage(350 km to an 90 litre tank) have done all the basic things it could be like maf sensor, plugs + wires, Fuel filter, and air filter. I’ve heard talk about it being the cats but they are relatively new and got no codes, and help would be very appreciated!

[sefiroxx]

Run a scanner and check if:
- changing from open loop to closed loop
- check o2 readings and confirm if STFT and LTFT are in spec
- check temp readings

may have a stuck injector. So a fuel pressure leak down test, should hold pressure for a bit after key off. If not, injector could be leaking. (Also, could have led to cat failure as fuel would end up on cat)

[chevypower102]

Have you tried replacing the cap and rotor? How many miles on the truck?

[Colossus]

No cap and rotor.  It has ignition coil packs. 

[Mace]

Would I need a high end scanner for that open loop test, and turns out I was wrong the one cat is bad and I think there’s nothing left inside, oops. Got told a misfire is making my cats burn up. Appreciate the help I’ll get on that ASAP