I'm running a standard precision t3/4e. I have a -3AN line, and smoked like a chimney after getting on the throttle and then letting off.. like at stoplights.
So, I bought a new oil inlet flange with a restrictor (1.6mm) from Ebay. It's made by function-7 (
www.function-7.com) and took care of that smoke issues instantly.
If you don't have a smoking problem, you don't need a restrictor. If you don't buy the function-7 flange, you will have a very hard time finding a -3AN oil restrictor. -4 is what they're made for. -4AN lines have the restrictor inline, via filter with restrictor, or at the F7 flange.
Then again, you can build your own restrictor too.. thread a -3 male-male fitting, insert a hex set screw, and drill a tiny hole through it. That way you can tune the hole size by changing hex set screws.
-Jeff