So after multiply attempts at multiple different things, still cannot get my p38 4.6v8 gems to run smoothly, found that by clamping off the fuel return line the car would run mint, few readings, fuel pressure ignition on, 37psi then drops to 34psi, and stays, once started, it’ll drop to 29psi then climb back up to a max of 32psi, if you blip the throttle it’ll climb to 35psi no more, if you apply throttle steady it’ll drop down to 25psi and slowly climb and start to miss fire again, with the fuel return line clamped off it runs mint and smooth but fuel pressure with climb to around 60psi which is far too much, passenger side o2 sensors read 0.3v and drivers side read 5.0v with multimeter, on the scanner they both say around 0.14-0.60v ish replaced fuel pump, filter, pressure regulator, o2 sensors, along with a whole list of Other bits, only other thing I can think is maybe the injectors, any idea on a way to test them correctly? I’ve had them out and checked for clicking and seem to be okay, and tested loom with a noid light and again all are blinking as they should be

So I’ve have to make another account, last one wouldn’t let me log in, I’ve got a 1997 p38, little under 58k miles, having all kind of problems, replaced a full list of parts, still stuck, I’ve read online today that the fuel temperature sensor have a fail safe of 40’c mine currently reading 42-46’c, if I slightly clamp off the fuel return line the car runs perfectly, if the temp sensor is in fail safe mode, would that cause it to drop in fuel pressure?
Had it on the emissions tester today and the lambda reading was through the roof, co and hc were in spec, when you let off the throttle it initially came back within spec then instantly fall out again