Hemi piston slap?

Here is the problem and I have it also with my LS, It's carbon on top of the pistons and when cold the carbon is hard, the piston makes contact with the head cocking the piston and making the skirt slap the wall. When the temp comes up operating temp the carbon gets real soft and you don't hear it. You can fix it with water injection when hot. If you get the motor to operating temp fix the throttle to run about 2500 RPM find a vacuum hose you can use to suck up the water, you need to restrict the hose to about 1/16" hole and stick it in a bucket of water and let it run, when the carbon starts breaking up it will smoke bad but it is normal and wont hurt any thing as long as you keep the water flowing through a restricted hose. I would start with a quart of water and see if it does the trick. Check the oil level before and after and check for water in the oil, you shouldn't have any if you inject it slow. Take it for a fast run down the highway when finished. Change the engine oil if you think it has any water in it. It may take a couple times to get all the carbon out. I worked for Cadillac and in 2003 we had to do this for the same reason, then they came up with another contraption to get the carbon out, it didn't work any better. Then came the piston change to a new design. I changed the pistons in about 50 Northstar engines, That fixed the problem.