Unit, A fouled ACT left me stranded at work. When I started the car it would idle okay, but once I got going it wouldn't let me get enough RPMs to get moving and then it would stumble and backfire.
Unit's right about your injectors probably not injecting. That's why I questioned it. Some people may actually have probed the wires to see if they were getting voltage.
That sound is the fuel wooshing through the fuel rails from the fuel pump running. You're correct that the fuel pump running shouldn't hurt anything since it does run all the time when the engine is on.
What did you replace the fuel pressure regulator with? A stock replacement or an adjustable? Did you remember to hook up the vacuum line to the FPR? If not, you'll run very rich at idle. The computer won't be able to adapt, either, since your relative fuel pressure will not be constant.
Give us a run down of your modifications and the events leading up to this problem? We don't know if it just started doing this one day, or you had some driveability issues that kept getting worse and worse. Did you do anything under the hood before it started doing this? Is your SPOUT connector installed?
The worst part of diagnosis is that there can sometimes be multiple problems that cause the same symptoms.
Unit said that emissions stuff probably isn't the cause since they don't come into play until the car is warm and at part throttle. That's true, unless there's a defect in one of the components or someone accidently hooked them up wrong.
Say, for example, you accidently hooked the EGR vacuum line to the FPR and the FPR line to the EGR. The EGR would get opened all the time because of uncontrolled vacuum and the fuel pressure regulator would be getting zero vacuum since EGR vacuum line is controlled and closed at idle, creating a high relative fuel pressure and a rich condition.
Another possibility is an EGR valve stuck open.
If you want, meet me in the chat room and we can discuss some possibilities. It may speed up the diagnosis process. I'll just login there and look for you. I'm at my computer doing stuff anyway.
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351W 89 Mustang GT Convertible