So here's my issue hopefully someone can help me with im getting codes 42&43 it runs perfectly at cold temps but once it warms up and I get it to highway speeds my rpm gadge will jump all around and 5 seconds later I'll hear a pop from the intake and it will loose power looks like my gadge cluster will shut off then I'll let off the gas and it will all come back no issues at all going up to 40 need help figuring this out

 

Please post the vehicle details for better help!

 

It's a 91 chevy k2500 305 4x4 efi

 

All I can offer up is the definition of ODB 1 codes 42 and 43, from my Haynes manual:

42 - Ignition Control Circuit (shorted circuit):

Check the wiring and connectors between the ignition module and the PCM. Check the ignition module. Replace the PCM.

43 - Electronic Spark Control (ESC) system

ESC module is not receiving a knock signal from the knock sensor. Check the knock sensor or the ESC module. Have the module checked by a dealer service department.