I have a few questions about the oil restrictor, I have upgraded to a top mount turbo manifold (custom fab'd) and a t3/t04e (.63 stg 5) turbo standard bushing turbonetics. I know it's a turbo designed for way bigger engines but I already had it and used it on the KA24 setup I had.

My question is why do we have to run an oil restrictor on the braided line going to the turbo when the factory turbo didn't use one? Or does the factory t25 have one built in?

Also question #2 what is the thread size and pitch on the inlet on a t3/t04e I tried 1/8" NPT how-ever that was too big, oops??? Just curious if someone know?

Setup,
S13/S13 REDTOP
custom top mount manifold / T3/T04 (Beast turbo, eventually gt35r)

Oil restrictors are for ball bearing turbos. Its to prevent the oil seals from blowing out as they require less pressure. You have a normal fluid bearing turbo, so you DONT want to use a restrictor.

My question is why do we have to run an oil restrictor on the braided line going to the turbo when the factory turbo didn't use one? Or does the factory t25 have one built in?
The stock setup does have a restrictor, it's built into the banjo bolt that threads into the block.

The factory banjo bolt isn't much of a restrictor. A ball bearing turbo runs a 0.03" restrictor. Call up turbonetics and see what size restrictor they recommend if any, and if its close to the diameter of the stock banjo feed bolt then just use a banjo to -3an for your oil feed from the block so you can reuse the stock bolt.

The factory banjo bolt isn't much of a restrictor.
Look again, it is about the same as most restrictors for journal bearing turbos... 0.063" roughly

A ball bearing turbo runs a 0.03" restrictor.
Yep, that's the standard size for most ball bearing turboes...

If you read his first post, he states t3 turbo with standard bushings... I'd assume that means journal bearings.