Yeah its true. Twin carbs guzzle fuel like mad. They can NEVER be tuned to meet any enviromentally saving ways. No matter which carb from WEBER or HOLLEY, its hard to get quick response like 4 throttle. If u have both a crab and 4 throttle assembly side by side, you would notice how little mechanism if on the 4 throttle.
For carbies, u basically have to worry about matching the ignition system. Where the 4 throttle is from ECU that controls fuelling and ignition. Well it depends on if you have time to tune the carbies to your needs. A carbie is more of a mid to top end power device if you ask me. And a 4 throttle is almost balanced out.
Cost i would say a low RM800 (lucky find) to a high RM2500 for WEBERS. And if u are even lucky to find a manifold adapter set to go with it. Else expect to pay more for the adapter manifold. And to mod a EFI engine to carb based, spend more again on the ignition system. Which in return a black top transplant seems very cheap already.