I asked the same questions about zoomies and found very similar answers about them EXCEPT when it comes to big cubes and nitrous. I also spoke to Tim at Fabshop and we discussed the use of zoomies on my 622ci bbc and the amount of nitrous I use and we came to the conclusion that I would not notice any difference between a nice set of 4 to1 headers or a set of zoomies and he was right. My car did not change at all as far as performance. I did lose some weigh and they do sound cool. I like the zoomies on this motor but any thing else should use a good 4 into 1 header that is matched to the motor.