I already searched and found many results but i have a gm t3/to4(IHI) turbo i believe and when i bought it, it came with a stock oil feed fitting already (-8an) and i know everybody recommends a -3 or -4 an feed line but the stock fitting is telling me to use -8an which is just huge. I have already ran this turbo with much smaller(-3an) feed line but the turbo seems to respond different every time i boost and it would build boost in different rpms every time and depending on how i drive it. The turbo has no shaft play and doesnt leak also spins freely.

 

so whats the question? I think most use -3 oil feed lines and also -4 with a restrictor

You could possibly try using a restrictor fitting with your feed line, but I would just buy a smaller line. You don't want to blow your seals