1998 TOYOTA TACOMA OVERDRIVE BEHAVING ODD

I have a 1998 Toyota Tacoma that has been babied and well maintained.
He currently has 260k Freeway miles on him. The issue has been the
overdrive. It works fine and slips in and out of overdrive with the push of a
button and has never had any hiccups. However I always have noticed that
braking in overdrive increases the braking distance. With overdrive off, the
engine feels beefier and braking is done without issue. OD also is sluggish
in acceleration (once again with OD off the truck accelerates fine even
without ECT enabled).

On the freeways, I always use OD (unless it's a steep grade as the manual
suggests) and I can easily reach 110mph without issue. I;ve had the
transmission checked, the master cylinder and brake booster are brand
new as are the brake pads. The manual states never to use OD when
hauling, towing or carrying heavy loads. I once thought this was to prevent
transmission "searching", but it definitely feels like the truck has a lot more
raw power with OD turned off. Am I imagining things, or could there be an
issue with the OD?

Also, I've always been curious if anyone has ever kept ECT on the entire
life of the truck. I think I have only used it once in the truck's history.