The engine flush is really a solvent which will thin out your oil and could drop the pressure even more so be very carefull using that stuff, it your pressure drops more dump it out fast. After you dump the flush throw in some 20-50 weight to see it the pressure comes up some, 20-50 is great for old tired motors which have more slop in them because it will help fill those worn clearances, boost oil pressure throughout the engine, and even quite some valve train noises. (It wont sqweeze out from between moving parts as fast). Your pressure should actually increase when you rev the engine, if it drops you are throwing oil out somewhere preventing the pressure from building, assuming your gage & sending unit are good. You might try replacing your oil pump before you pull the bottom end apart. When you spin a bearing the oil holes in the bearing no longer line up with the supply hole and the oil pushes out the sides of the bearing, when the bearing begines to spin with the crank it also disintegrates fast and you may see some gold color flakes in your oil since they are normally brass or bronze material so look close at your oil by pouring it through a coffee filter. Once this starts your time before seizing the engine may be limited if you cant keep enough oil pressure to other componants. Confirm your pressure is really running low with a mechanical pressure gage screwed into were the sending goes. A 20-50 weight can buy you some time if it helps raise the pressure.
