1993 c1500 4.3L Motor Problems

at heavy accell. There will be a knocking sound from the motor

seems like when truck shifts into 3rd gear it happens the most

and if i cut my wheels all the way to the left or right, the motor seems like it wants to die out... any clues as to what the problem might be ?

My haynes manual offers this......

PINGING OR KNOCKING ENGINE SOUNDS WHEN ENGINE IS UNDER LOAD......

1-Incorrect grade of fuel. Fill tank with fuel of the proper octane reading.(Could be bad gas in general. Are you in a cold area? water in gas might be an issue also.)

2-Ignition timing incorrect.

3-Carbon build-up in combustion chamber. Remove cylinder heads and clean combustion chambers.(Pull spark plugs and check for heavy deposites, or try a compression test, that might tell you if the combustion chamber is "smaller" than what it should be. If heavy carbon build up found, before you spend the high dollars/much time and effort to pull heads, first buy fuel a fuel additive made for cleaning combustion chambers and run it open throttle on the highway for a couple of minutes. If that doesn't work, then pull the heads.)

4-Incorrect spark plugs.(Check brand/type-word has it that AC delcos and NGK are the best, don't get champion. Also check condition and for proper gap)

Let me know what you find.