You won't really see difference in peak HP from EFI to a carb - IF they're both tuned right. The best A/F mixture for an engine isn't going to change, regardless of how the fuel gets in to the engine. Where I think you'll find an improvement is going to be in low-speed torque and engine response, and a lot of those functions are in spark control.

Where EFI shines is in driveability and emissions control. Those two items will help tame an engine with a big cam and low manifold vacuum, or help milder engines burn cleaner and get better mileage. A sufficiently sophisticated carb that was properly tuned might be able to pull off those same goals, but it would be tough.

The cost difference is tough. For a lot of folks, it won't be worth it, especially on a toy car that doesn't see the road much. However, if you really want to drive your race car on the street, or if you really want to hop in your small block A-body year round, rain or shine, EFI can help get that done. It might also be worth it if you just like tinkering with stuff and getting to know how your engine is really running. That's my excuse.

Clair