when i start up my car (90 240sx) it shoots out a puff of greyish smoke
and when the car is cold it has smoke coming out of the exhaust…
after it warms up teh smoking goes away…what could this beee?
oil?
Valves guides. it likley smokes while engine braking aswell.
^^ Yup.
Valves guides. it likley smokes while engine braking aswell.
how do i fix this problem?
Pull the head and replace the valve guides.
lol
Yup.
dont you mean valve seals sir 
I would replace both, if nissans have both and they are both replaceable. Eather way your going to end up pulling apart your whole valve train… Its a prefect time for a port and polish / new valvetrain 
Right. 
the valves are impossible to get off! loll i tried and cant get them off i broke
a socket wrench trying it
LOL