Above posts members asked about the benefit of Webers. An IR system gets close to Fuel Injection systems that have a butterfly on each port. If you consider the fact that a 4b carb and manifild spend a lot of time sucking exhaust gases out of one exhaust port and into another cylinder as it's filling up, an IR system with Webers eliminates that and can let you run more duration while maintaining a good idle. At the top end Webers are probalby not that much more HP than a good 4b setup, but in the low end and mid range the results can be much better than a 4b.
(At least that's what I've read
Regards
Jim