HELP ! smoke in my exhaust and start problem !

[finetuned]

Hello everybody, just joined NICO ,

i am in the process of buying a 1991 300zx TT with after market z1 turbos, intercooler piping, and BOV, there is black soot on the hks tail pipes, and also blue smoke coming from the exhaust ( oil leak some were, and if you look under the engine bay you can see evidence of a slow oil leak). im not sure if exhaust smoke occurs on acceleration or deceleration, or even under turbo load. and then there is the starting problem, when engine is cold it starts right up, then once engine warms up turn key off then when i go to start the engine back up it cranks and turns over but will not fire, and when it does the idle is rough and studders.

p.s. found a "D" shaped brass looking gasket not sure what it goes to please help

things i think it could be
idle air controller
needs a tune on ECU for bigger turbos
sticky injector
fouled plugs
maybe 02 sensors / Catalytic converter
oil leak from mysterious gasket ruined some of the parts above




any help would be greatly appreciated