the biggest con to the carb is that you have to buy it, and spend time tuning it.
there are also a bunch of other things you need to buy to get it to work.
you need a low PSI fuel pump, a regulator, intake manifold, the carb, jets, air filter, etc etc. basically take the price of the carb NEW and double it.
there are basically two styles of intake, and two styles of carb.
the street setup, is the RB upper intake and side draft carb.
http://www.racingbeat.com/RX7-1986-1...ake/18101.html this keeps the stock lower intake and 6 ports. since the intake is long like stock you can expect a nice broad power band.
you can also go IDA, which is a downdraft. intake is shorter and straighter, so top end should be better.
http://www.mazdatrix.com/r-idamanifolds.htm