Regarding headers, if running low boost 6-8 psi, standard manifolds should be fine. Running higher boost you need to eliminate exhaust restriction as the turbo itself will start creating high rpm restriction and impact boost pressure as the engine has to overcome the pressure build up in the exhaust. Sizing a turbo is usually walking a line for best fit.

You will need a bung in the exhaust to mount the wide band AFR sensor which is completely different than factory narrow band sensors. Your boost sensor should be plumbed in the manifold after the throttle body. NEVER tie into the brake booster vacuum line. Also, use a vacuum manifold block to supply the vacuum reference for gauges, any electronics, BOV, etc.