92 Stealth SOHC help

So i bought a 92 stealth base model, it has been sitting under a tree for 10 years or so, I have been going through the car gradually replacing whats been dry rotted ruined etc... However.... the previous owner right before i bought it, replaced the fuel pump, or so he said.. Well my fuel pump starts whining in a strange way so the first thought is bad fuel pump right? I open up the fuel pump area in the trunk, prepared to use the guide on fuel pump removal to take it out and inspect it. Well as soon as i open it up, i notice the blue two way valve is missing on my car. The previous owner put new fuel lines in and i believe he just removed the valve completely and ran the hoses straight together. My question is, would the two way valve cause the fuel pump to make a surging whine and cause issues idling? its not a constant whine, just a surging whine with a break in between of roughly 2-5 seconds. The noise doesnt pick up speed with rpms. Picture included, i took a picture of the busted plug i found as well, so look behind it and see the two hoses just ran together.
Attachment 7859

bumping with video of the sound. I also discovered the fuel pump is a new walbro. if it helps any.. https://www.youtube.com/watch?v=qTgg94yAKek

what's the fuel pressure?

I havent been able to test the fuel pressure yet. however i did check the engine code and it said coolant temp sensor. So i changed out the ecu temp sensor, however even after unhooking the negative terminal for several minutes, with the brand new sensor, it still reads the same code.

definitely check the fuel pressure.
if you're getting coolant temp codes - have you checked the thermostat? take it out and toss it into some boiling water. does it open?

It will take me awhile to get my hands on a fuel pressure tester, i will post results when i do. However, i believe the fuel pressure is fine. once the car is running it has plenty of healthy power so long as i keep my foot on the pedal, however when i let off the rpms drop heavily and it dies. when its first started up in the morning it will idle by itself for awhile, but when i give it gas and let go it dies. The fuel pump sounds as if it builds up pressure into a high pitched whine then immediately drops back down and builds back up slowly again. Could it be the two way valve the previous owner removed and ran straight hose near the fuel pump? also, i can check the thermostat eventually, but i know its opening up enough to let the radiator itself get pretty hot.

I solved the rough idle problem, when i bought the car i immediately cleaned up the throttle body but all i did was spray it down and out. Between that time that it sat for me to fix everything else, the pcv valve let enough oil in to the throttle body it had gunked up even more, so i went in and instead of spraying it out i actually took the throttle body off and disassembled everything and cleaned it all scraping brushing wiping etc.. However, the engine coolant temp sensor code is still showing. after i installed the new one.