I have a noise on the restart of a warm 4.8 engine on my 2003 silverado. I have changed the oil at 2500 5000 and 8000 mileswith mobil 1 synthetic, the truck now has 8000 miles on it and the noise started after the last oil change. there is no noise on cold engine start and the noise isnt too loud when stopping and idling for a short time with a warm engine, then slowly it gets louder.It gets really bad when you let it sit for 10 to30 minutes and then start it. The sound is most noisy for the first 10 seconds or so then slightly quieter.If you rev it up slightly 2 or 3 times then let it idle the noise stops for about 5 to 10 seconds then starts up again. I have read about the O-ring on the oil pickup tube being bad on some engines with similiar symptoms as mine. Ive read one complaint exactly like mine but he did not have a solution. GM is going to change the O-ring, Im not totally convinced this will cure it. any answers would be appreciated, other than that problem I love my truck.