The GM tablets have settled into the combustion leak in my 93 6.5. includes the 99 on up to the 580 over altamont pass. Gauge to the left of the middle like the old days. Next test the grapevine.
And are a Bandaid on a sucking chest wound. This is temporary at best and WILL eventually fail, most likely at the worst possible time, and you WILL wind up replacing both heads as a result - if you haven't damaged pistons or cracked the block as a result of the catastrophic failure.