I have a couple questions.. I have a 91 fc3c. would it be better to run a true dual exhaust or a beefy single? I know the dual would have an increase weight compared to the single but air flow would be better. Can I even put a true dual exhaust on the vert? And final question.. What is this tube here for? What does it do? is it essential to have if I swap a new exhaust on? I was looking at racing beat exhausts. Does anyone here have any reviews on them? What should I look out for if I use a custom exhaust?

 

That tube is from the airpump, it pumps fresh air into the cat to help clean the exhaust gases. Emissions and whatnot.

 

This has been discussed many times. This should get you started:

RX7Club.com - Search Results
RX7Club.com - Search Results

Each has their benefits and it also depends on the port. True dual is good for stock ports. A long primary system seems to be the best but will have to be custom built and also tuned on the dyno to get the most power out of it. Though it sounds like one can get pretty good gains from lengths that are floating around out there. Also really need a standalone as well for max performance gain.