1995 Ford Explorer Oil Pressure Drops

Does the vehicle idle rough? If so, possibly a vacuum issue if the rpm's fluctuate and could cause light to come on. But, most likely, if you replaced the oil pump and still doing it, the oil journals in the engine may be blocked from oil sludge causing oil to not flow properly throughout engine. My first step prior jumping to an oil pump would have been and actually was is to do and engine flush. Pyroil makes a product that prior to changing the oil, you run vehicle till engine oil is hot. Pour in Pyroil engine flush into old oil and let it idle for 5-8 minutes. This will flush out old build up in journals,tensioners,etc... that a mechanic cannot see. Do Not drive or rev engine, just let it idle! Replace engine oil and filter, I use Valvoline Maxlife oil religously. Not only did I get normal oil pressure but also better fuel economy and engine performance. I do this @ every 30,000 miles and currently have 128,000 with no oil problems.