My understanding is that HKS ball bearing turbo's (GT3037) have an internal oil restrictor and therefore does not require an inline oil restrictor. My tuner recommended that I should install one anyway since my oil pressure is around 90psi when cold and 30psi when oil temp is warm.

To me this makes no sense as a restrictor in the turbo or in the upstream line provides the same result.

Garrett's faq says it should be around 45psi for BB turbos under load.

Thoughts?

 

I have the same oil pressure on my motor and no problem.
I do have a inline oil filter for the turbo oil feed line that have a restriction built in but not necessary

 

I would run a restrictor inline unless you are 100% positive that the turbo has one built in.