copstop350

sorry fellas for the probably stupid question but where is it located? is it located on the bottom of the block behind the base pan? my oil pressure in my 99 4.0l is really messed up. Reads 3 on the gauge when start up cold and when it warms up after a short drive when at idle it drops until the "check Gauge" light comes on. I read that it could be caused by blockage in my pressure relief causing oil to circulate to freely and not allowing pressure to build? also at 2000rpms driving its reading about 1.5 and than when you kick down into OD it goes almost to 3 again. anyone with any anwsers it would be greatly appriciated!!
thanks