They will for sure make power (it my be a very little increase) if they are clean flowing (no lip restriction) or they flow enhancing. Increasing the space or distance between the carb and runners allows for better atomization. But you can only go so far.
As for an adapter or riser get flow enhancing type... And I say flow enhancement because both adapters and risers nave all different kinds if inside machining. Such as a strait adapter plate would match the carb square base plate and pass strait through to the intake. vs. High flow adapter which will be machined to match the intake bore and the carb base and then the machining in between can be a polished and rounded, like the one I have. Risers have the same options in such that they are matched for a specific situation but the machining as well as material can make a big difference. I had a thread about spacers and adapters a while back and there was a lot of good info.
