1999 Silverado P0305 Misfire and engine knocking ????

[TLB63]

Driving to work one morning slowing down for a red light, downshifted from 5th to 4th not using the engine to slow the vehicle, light turns green I go into the turn and it feels as though someone threw a chain around the rear axle, the truck jerks but continues to run, along with the engine light flashing. I drive about 3 miles, stop and check the code with a code reader, I get P0305, I go home that evening change the plugs and wires thinking i may have fowled a plug or broke a wire, change these items start the vehicle and i notice a knock in the engine. I have since tore the engine down looking at bearings etc. but have not found anything. What am i missing. Any assistance would be greatly appreciated in this matter.