As said around 300hp is about what that cis will run safely. Maybe a bit more. I ran a hob switch to switch to full throttle enrichment when going into boost. And made a small adjustment to the eha for more fuel. That is a very delicate adjustment though. More than one throw away eha to get it right.
Also that is with all good near new quality working parts. Which these days cost more than an aftermarket fuel injection system.