if i were to put a turbo on my 91 formy do i need to have the turbo running off of one header then the other header running into the downpipe with or w/o a cat? and should i run a dual outlet exhaust? and what would be the best exhaust for this modd?

You run both headers to the inlet of the turbo, and have a single pipe out of the turbo, that needs to be run to the rear. There's no reason to run duals. And you are planning to run a cat? If you have emissions, will the turbo pass... definitely not a "visual".

i dont have to pass emissions so im good...and if i have both headers running into the inlet of the turbo and 1 pipe running to the rear from the outlet then how do i get my intake??/ that defeats the whole purpose behind a turbo...

A turbo doesn't blow exhaust gas back into the motor. The headers must lead into a common piece of tubing if you are only running 1 turbo. This enters the turbine housing and spins 1 fan which is connected via a shaft to another fan in the compressor housing which then pressurizes air to shove into your motor. After spinning the turbine fan, the exhaust gas exits the housing through a downpipe that is the beginning of the post-turbo exhaust. On the other side, as the compressor fan is spinning it is drawing air through the turbo's inlet. This is the air that finds its way into your motor, not the exhaust gas.

All that make sense?