What engine is this (6 cyl or V8)? Why did you change the oil pressure switch? How many miles on truck? Is check engine light on?
A sound like that under acceleration could be engine ping caused by carbon build-up in the combustion chamber.
This engine has decently high compression ratio, but the adjustable cam position is capable of modifying the dynamic compression to keep it from knocking or pinging.
Remember that these engines are perfectly happy with 87 octane fuel that would normally melt another engine into a blob of liquid aluminum. This is because the exhaust cam timing position is driven by the PCM ...and for that reason they don't even need an EGR!
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