88 K5 Blazer

[Fabrimacator21]

What would cam have to do with ESC? Unless it's too far advance on the cam I don't see how it could be a problem. If it is too far advanced then just put it where it needs to be. No need to swap the cam unless it's running like crap.

My guess is a loose connector or bad pin or something electrical.

 

[Thunder]

Have you checked or changed the dist module? You said you have a MSD distributor? Their modules are problematic to say the least.. I have seen many of them fail or cause problems.
A bad dist module can cause a code 43 if there is an intermittent open on the EST port or wire to the ignition module.

If you used teflon tape on the threads of the knock sensor it will cause problems.

An exhaust leak on the header flange above the knock sensor can cause false KS signals

 

[Russell]

Have you had a scanner hooked up to your truck to see what the ECM is seeing? Definitely sends you off in a far more clear direction than just throwing new parts at the truck in an effort to sort out a horribly vauge code 43.

I once had a great deal of trouble with setting code 43 on my old 77 Stepside after switching it out to TBI from carb. Ultimately it wound up being a broken wire running between the ignition module and the ECM (white wire) It would work 95% of the time, but every once in a while that connection would break for a second and it would set code 43. All my diagnostics showed no problems with any of the circuits until I started getting desperate and started tugging on wires while checking the resistance across them.