The tests that "mechanics" do on the battery is a draw test. Over the 15 years I've been on here, it has become obvious: The battery can pass a draw test and yet, not do it's filtering job well enough.

Batteries have a capacitive reactance characteristic that fades with age, but not at the same rate that their current sourcing capacity fades. In cases of weird issuse like: BAS/ESP errors, powered wing acting "funny" or a power top that acts up from time to time, a new battery often cures the problem - even tho the battery "tests fine at the shop".

But I also think CL770's advice is probably as valuable as any I can offer. Go ahead, pursue the tune issues as he instructs - but just keep in mind what I've said about the battery. Let's see where this goes.