Dead battery but should be that way

1997 Tahoe, 2WD, V8. 107,000 mi.
First let me say I love my Tahoe but hate AC Delco. I've replaced the alternator twice, the starter, and the fuel pump. No other real problems except this one.
The starter and the battery are brand new and the gauge says it charges fine. However, if I park the car for more than a couple of days, its dead. Opening the door and getting in, I noticed a fast clicking, like when a turn signal flasher goes out (signals work OK) but the noise was happening with no key in ignition. Sounds like its behind the dash between the steering wheel and the radio. This is probably the short but can't figure out what it might be. Any ideas before I pay the pros. By the way, no code comes up.

Check Your Terminal Cables. The Rubber Around The Actual Terminal (the Metal Part) Gets In The Way Of The Connection. Cut Off The Rubber Around The Metal Part Of The Terminal. Clean The Battery And The Terminal. One Of The Two Postive Terminals Has A Spacer Nut In It. Save It. Re-connect The Bare Postive Terminal In The Same Order Using The Spacer. If You Get A Smaller Terminal Bolt, Like The Negative, You Can Trash The Spacer And Connect The Two Positive Terminals On Top Of Each Other Right On The Battery. Go Otpima Next Time.

I'll give that a look first. This weekend I will get the battery charged enough so the fast click starts again, then I will start pulling fuses one at a time. Perhaps I can isolate it. I'm thinking it might be a relay also so I'll try the plug and play on them, too.