I know ficmrepair has had issues with 58V and quit offering them but they are not the same as the BPD unit. They were overvolted/modified stock PS vs. the BPD all new PS and half shell that has been built to handle the extra voltage and heat. No one has shown to my knowledge any actual dyno numbers demonstrating 58V actually produced any additional horsepower, but many many drivers have reported better throttle response, easier starting, help with stiction issues, regrew hair, fixed their low testerone, helped them loose weight, cured their ED, and brought upon world peace.
All kidding aside I don't think it the Bee's Knee's when it comes to upgrades but I like the idea of overbuilding anything, until someone actually post up about a 58V unit doing any damage count me in
And while your at it get the FICM tuned. Pretty good bang for the buck on small horsepower and mileage gains seems to be the consensus