4v to 50v, sounds like a Ficm, or injector controller maybe?
The injector power supply in most european cars actually have 4 supplies, one 48v supply per injector, the Lm2577 is a popular chip, on eof these can only provide about 1a at 48v from a single 12 batt.
You need something more along the lines of a system that uses a smps Ic with a outboard switching device, maybe something like a Uc3842 controler chip & associated parts, such a project is reasonably complex and would be in the realms of a more seasoned hobbyist or pro.
You could try ebay, you can get step up supplies from china, current ratings are a bit optimistic, derating by 3 would be a good start.