Granted these spacers may not be the best bang for your buck , but the fact remains they do work given that they are used on the proper application, it takes some experimenting to find just what works best for your combo, you just cant buy something and hope it works u have to research it and make a informed decision and go from there. I personally use a 2 inch open wood spacer that works great and I also use a KN stubstack to further inhance the air speed into the carb. Ive never had the luxury of a dyno to prove that they work I have to go by numbers at the track and without these 2 items on my current combo the car slows. Horsepower is expensive sometimes but thats what I love about racing and working on cars is the tuning and tweaking to get those few extra horses its very satisfying to me but then again some people would rather sit on the couch and say it cant get no better so I'm gonna leave it alone or its too expensive, yeah right like u didnt just spend an extra 200 or 300 bucks on that fancy carb or a 1000 on them bad azz heads...lol whatever.