After having replaced my all but depleted battery I noticed a number of improvements re: nearly all electrical functions.

Windows zoom up and down. Garage door opener has gained 30' in operational distance. Interior lights are brighter as well as puddle lamps.
Most intriguing is the slight whine I had from the ZF6 when in gear; it went away mostly (when in neutral) but was noticeable while moving down the road.
Now I have no discernible whine in neutral or while at a stop in gear and the ZF6 sounds great.

What with cleaning the TB, cleaning the K&N air filter and vacuuming the critter crap under the filter the X350 has improved in performance significantly.

Seat of the pants driving tells me acceleration is at least +20% and I suspect every sensor is now getting proper input and sending proper output.
It's a shame I let the AF and the TB get so dirty. I've placed some 1/4" hardware cloth (sprayed epoxy black) over the air intake to eliminate hitch hikers and have a monthly reminder to check voltage across the battery terminals. So are these improvements placebo effects? I tend to think not.

Our automobiles depend on strong batteries as has been previously posted by numerous others. My experience confirms that and I encourage all you good folks out there to take a few minutes and put a DVM or VOM on your battery and look for about 12.6VDC with the battery at rest. With the alternator spinning I measured just over 14.5VDC. I'm comfortable with that number. Summer heat is tougher on a battery than winter cold. I intend to check the overall health of my AGM battery once a month going forward.

Have a great summer folks. I suppose you folks south of the Equator are preparing for your own seasonal changes, too. See you on The Forum.