I just bought a 1990 Mazda RX-7 conv and i am looking for exaust and intake but what brands where should i buy for the car any advise will help  

when it smokes, it should be white.  this means the apex seals are bad. this is normal/routine for rotary engines.  the FC is a great starter platform.  the motor isnt bad, it just needs to be maintained.  the apex seals will go out every 40,000-70,000 miles depending on how hard you drive the car (racing vs daily driving, mods etc).  its routine service to have the motor rebuilt every 60k miles or so. if you perform regular maintanence (prompt oil changes etc) you will see more mileage and better reliability.

even though the LS1 is a great motor , light, powerful, and the swap has been done before a couple times, please dont do it, for my sake.  its a sacriledge! swap a jdm rotary if anything, or even the FD twin turbo motor.  the LS1 swap will cost lots of money and time.  

its still just wrong...

my friend's FD makes over 450whp on pump gas.  i would take that over the ls1's modded 500hp just because you wont be able to get it to the ground in such a light car, since its torque is obviously wayy higher.

to put american muscle in place of a high revving twin turbocharged rotary into an iconic car such as the RX-7... makes me cringe.  but in the end, its whatever melts your butter.