Does the tapping increase with engine speed?
Talk to us about your maintenance regimen....oil changes on time, proper oil, etc...?
I think you may need to employ an inexpensive tool called a stethoscope. any autoparts store has them.....I have used a length of hose and small funnel in a pinch...but you basically put the end of the hose on different parts of the engine until you locate the tapping...(yes, while it is running....but PLEASE BE CAREFUL around the spinning and whirling bits)
Once you have isolated the sounds to where they are the loudest you can deduce whats wrong.
Use a second person to get in the car, and with their foot on the brake, put the car in drive, then in reverse, you may be able to hear whats going on when the "boot" is open.