Sealant is a must in the corners where the head meets the block for the LIM. The pellets are a totally different use case and is more of a preventative than a must and is personal choice. It's something that has worked well for me and for many others. Would things have been different if I didn't use the tabs or a stop leak in the system who knows....but if it seals up a weep starting around the water pump, welche plugs, radiator, a hose, and water to air/oil leak in the LIM or heads then all the better. It was more around the assumed notion that using stop leaks was bad and I raised the GM thing to make a point that the manufacturer recommended it. It's not a die in the ditch matter.
Sealant in the corners is a different matter. There's a physical void in that area regardless of the condition of the engine..........
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