True, it's just a booster for all frequencies - a passive TB Plus turned up very loud + some subwoof. The combo is much better than with the Bart pups on the (then higher-priced) Deluxe version. The TB Plus colors the Bart active elctronics rather than the other way around.
I'd keep it, but while you're at it, why not add a switch to deactivate it at your choice? At a gig with bad acoustics, an active bass can sometimes be handy***. Don't ever quote me with that!
***So is a passive switch if your battery has run out and you have no spare with you!