I was off on Monday. Went to the dump, and Home depot and I heard a tap,tap,tap from my 98 K1500 5.7 when I got home. Sounded like a lifter gone bad on the #1 cylinder. Used a broom stick to listen to the motor at idle and found nothing, it seemed to run ok. Tuesday morning it was still tapping when I went to work and I stopped at Advance and put a bottle Motor Medic in it.10 miles later it was still tapping. Went to go home after work and it was tapping when I started it. I shut it off and poked around the 5.7 and found the #1 spark plug boot was all the way off the plug. Stuck the boot/wire back on and no more tapping, I think the noise was the spark jumping to the plug, it ran the same. I had changed the oil about month ago and I dumped it when I got home. The oil was black but it did not smell like gas. I guess the motor medic washed cleaned the motor good and it's running smoother than before.