do journal bearings need restrictors? i've done alot of reading, and found just as many different answers

how do you know if you got too much or too little oil? the oil feed inlet on the turbo core is 4mm. my oil lines are around 4.5mm - 5mm, tee'd off the oil pressure fitting. has approx 80psi when cold at idle, once fully warmed up it'll drop to around 20psi at idle, and peak at around 70psi when giving it sh*t. drain line is whatever the factory size for the t25g is, and enters the sump at the very top.
does this sound about right for a t25g? should I fit a restrictor, or could the lines be bigger? (probably no point though, if the core only has 4mm inlet right?)
any input is appreciated.
cheers
-matt