I've been running my FiTech with a Walbro 255 for 3 seasons now. Very early model 30001 600 non PA. No issues.
Hooking it up dead head without the regulator for testing purposes should be okay. It'll tell you if the regulator you have is bad, which is what I'm leaning towards. This way shouldn't present a problem for the FiTech unless you're bypassing more fuel through the return and starving the head unit.
It's not as nice of an install because you have more fuel lines to worry about, but I use this setup in mine as well as my wife's 71 Chevelle that we just put a 30003 on.
http://www.tanksinc.com/index.cfm/pa...rod/prd548.htm
It just flat works. Yes it's soft line and I'm sure that some will have issue with that, but as long as it's inspected regularly and replaced as necessary, there shouldn't be issue there.