I am using MS2 and an Innovate LM2 WB kit on the RV8 int Serp for tuning but generally run open loop now my VE table is so well soughted (no cat) paid for TS and MLV
Bullit proof power unit, the only weakness i know of is they like a water pump these motors will do 100's of thousand of miles with just routine servicing typical Jap gem
Worn cam bearings and worn rocker shafts & rocker arms may need investigating,although not necessarily in that order as the cause of your lost oil pressure.