Have you tried playing upright style whole side of index finger bent at first joint from knuckle? My MIJ with original pickup sounds like an upright this way. Did change to a Muy Grande. Other wise it sounds like it sounds keep it or sell. If you had a Jazz you wouldn’t be saying it doesn’t sound like your single coil or split coil P. Elixirs give a phatter harmonic content. They made me keep a ‘57 ri. Made it a new bass. My tech would say put your ear to the horn and also listen to it acoustically. Is that the sound you like. If not, don’t chop, sell. I was posting pics to sell my ‘57 because it failed that test. Then the string change to Elixirs and Voila! It’s a daily player.