Vortec 350 Engine noise

I have an 98 Silverado Pick Up with Hypertech Programmer and K&N Stage II Filter System. While accellerating with low rpm i hear noise from the engine, when i lift
the pedal its better when the rpm increase - no noise. something to be worried about????
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What kind of noise? Knock, ping, bang, thud??????
Doc

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Sounds like "pinging" caused by excessive timing (BTDC) at the lower rpms. You may have to reprogram or better yet go back to you original timing to see if the noise goes away.
Hope that helps.
-Omar

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