Hi Mike, sorry I didn't reply to this way back! KF engines have very low oil pressure at idle, that's normal. Most of them I've seen behave as you describe. Yes, worn bearings will cause low oil pressure but if the bearings, especially the rod bearings, are worn you'll get engine knock. The rod bearings knock pretty loudly whereas main bearings will be a low pitched metallic knock which is most noticeable when you accellerate. If you have bearing knock, you will know it. The pressure relief valve mainly effects the car at higher rpms. You can stretch the spring out, however, the shop manuals recommend changing the tension by adding shims because if you stretch the spring out too far, it's very difficult, if not impossible to shrink it again. The pressure relief valve allows oil to bypass the pump at higher RPM so that you don't have too much oil pressure when driving in higher speeds. If it opens too soon, pressure will go low. The purpose of the shims is to put more tension on the valve so it takes more oil pressure to open it so yes, it will mainly effect the oil pressure at higher RPMs. If you make this adjustment, you can use washers as shims. How many? It's hard to say, trial and error might be the only way to know for sure. Put two in, if it's now too high, take one out etc. Hope this helps.