Heavily customised MB-4. Basically replaced most of the hardware 😛
First thing I did was change the strings (before I changed to flats) which made a huge difference to sound and output so would strongly recommend.
Hipshot MB6 Lightweight tuners, barely any neck dive now when sitting.
Brass nut
Brass saddles
Dressed frets
Artec SE-2A Preamp with rear battery
La Bella LTF-4A Flexible Flat wounds
Series / parallel switch
Rear mounted flush jack input (have always loved this design on Charvels and wanted to try it)
Sanded the neck for a better feel (and kept going because I liked the look. Bit of pink sharpie and I ended up here :p)
It now sounds and plays amazing and I have no want for a more expensive bass.
I tried the Warman pickup and thought it sounded way worse than the original, which I never had a problem with tbh
Need to fill the old tuner holes but haven't got round to it, will never like the look of the tiny tuners but the weight was worth it to me.