Knocking noise

I have a 2000 jeep cherokee. I has about 95,0000 + miles on it. I can hear a knocking noise in the engine. The noise becomes less apparent when i let the car sit and warm up. I've tuned it up and given it an oil change. But still no change. Does anyone have a clue to what this may be? I'm afraid this might be it for my baby.

Could be piston slap.... is it real loud? or does it change when you gas it hard?

Yes, if you press on the gas it gets really loud. However, if the car is warmed up for awhile, the noise is less apparent. If I don't let the Jeep warm up, it sounds like someone is hitting the car block with a crowbar.

Does the noise sound low like in the oil pan area (rod)...? or in the middle of the engine ( piston slap) or the top of the engine (lifter)?

Are there any metal shavings in the oil?

I don't see any metal shavings in the oil. It does sound like it is comming more from the middle of the engine. Is piston slap serious? Curable? Like i said the noise is less apparent as the engine warms up. The less I let the engine warm up the louder it will be.