i have read about piston slap ... does it more when cold and less when warm usually . my car is having a rattle after it warms up and it hard to tell from where , upper region i think . it does it at idle and almost immediately stops when i give the motor fuel . when the rpm climbs above 1100 it stops and sounds like the sweetest thing i know . my gauge is reading good oil pressure and it seemed to become more noticeable after i switched to amsoil 5W30 . car is the ls1 with 39000 miles . you have probably heard this question a lot but any info would be great . thanks guys .