engine noise

Can anyone tell me if they have had the same stuck lifter noise in their truck or not? its an 01 4.8. i have the usual piston slap noise at startup, but while its running theres still a tapping.its not a bottom end noise, like a bearing, its definitely up top.a friend has 2 LS1 trans am's, and has the same noise in one.i have heard that these noises are common on LS type engines, but ive also heard that oil additives are a no-no with them.is there an additive thats safe in this engine that can quiet it? because im not gonna to just put STP in it if these engines shouldnt have oil additives. any help would be great

you can put thicker oil in. 10w/30

It's the dreaded piston slap problem..My 02' makes the noise anytime the engine is running...I use 10W-30 Amsoil in mine, it doesn't make any difference...

The sound should go away after the engine runs for about 30-40 seconds.
I know mine does. and it only happens when it has been sitting over night.