alright here's the story...
I installed a Walbro 255lph, works fine. Sounded weird at first but I am totally certain it works. I also installed a Vortech 12:1 FMU. Since my car is a '95, I removed the stock fuel return line (from the driver's side of the fuel rail), ran a length of hose to the FMU which I'm putting on my passenger side, and then ran a length of hose back to the stock fuel return hard line, which is a steel line on the firewall. I used fuel injection hose clamps and yadda yadda yadda throughout. The hose is the same inner diameter as the stock hose, but has a greater outer diameter.
Yesterday, I got the car started, and it was running pretty well, I was more focused on the wicked hissing sound of the turbo, but then I realized that it was the hissing of gas shooting out onto the motor from the line where the rubber return from the FMU meets the steel hard line on the firewall. Shut the car off, not too much gas out there, I tightened up all the hoses and put this hose on as far as it would go and torque the clamp on ridiculously tight.
When I primed the car by turning the key to start today, fuel leaked out of the rubber line under the car, where the big rubber line from the tank (19mm wrench) meets the smaller line (that you use a 14mm wrench on), even though I was certain it was tight when I reinstalled the new pump. I tightened it as much as I can, to the point the 14mm wrench slipped a bit, and this leak went away.
However, when I started the car it was idling rough. I was like "what the fuck?" and revved it just a bit to try and get it a bit more gas, but then I heard a waterfall sound and looked under the car to see a copious amount of gas oozing out from behind the motor. So I dove for the ignition key and shut off all the electrical stuff in the garage.

It is leaking from where my new return hose from the FMU meets the steel line on the firewall. The hose is on as far as it would go, right up to where the steel line bends 90 degrees and goes down. The clamp is on as tight as it can go, but it still leaks a lot of fuel out of here.
My uncle believes that the steel line might have a hairline crack in it that would leak gas like I described, or that the vent line is plugged so the pressure is going through the feed and return line instead, which I am not so sure about. I don't have a fuel pressure gauge right now, I'm picking one up tomorrow, so I can't check and see if the idle pressure is abnormally high (which would indicate a clog somewhere, maybe in the return line like starturbotalon said).

Any other ideas what it could be? Are those steel lines easy to crack?

cole's notes: car insists on leaking gas from a connection anywhere between the send and return. a lot of gas, mostly from where the FMU return meets the steel hard line on firewall.

1995 Eagle Talon ESi

It sounds to me like something in the flow of the fuel is not plumbed correctly. You're saying it's leaking ALOT from the return line, but the return line shouldn't have a lot of pressure in it ... no more than 10lbs give or take. Your return line just trickles (sorta) unused fuel back to the tank that wasn't used in the rail. To be clamped as tight as you're saying and spewing fuel like that there must be a lot of pressure in that line coming from somewhere. What's going on at the end of the steel line back at the tank? Did you connect the return properly during the install of the Walbro? Steel lines can crack, esp since you've clamped it so hard, but I don't think that is your main problem ... there is something else going on. Keep posting w/ what you find out ...

1999 Eclipse GST 4G63

Alright, gave it another try today. I switched from the lines I had before to much shorter and smaller lines (I relocated the FMU to right underneath the throttle body), these ones are the same inner diameter as the stock one was (the other ones were slightly bigger). Still leaked. The car idles fine, ran nice and smooth, a little leaner then it usually does on start up, but it still leaked a lot of gas out. Not as much this time, we spotted it in time Its still a rather large amount of gas to spill in such a short time though.
I don't have any tools to investigate further, so tomorrow I have to take the car and let my buddy work on it in his shop. Hopefully I'll be able to drive around with turbo power before the end of the week.

1995 Eagle Talon ESi