[Z-linkCobra]

Do you have the plexiglass inspection hole plugs? If you dont go find you some so you can see what its doing. Sounds like to me you tried everything I would have suggested but I want to lean towards your fuel pressure rising enough to over power the needle and seats. Do you have a way to put a temp. fuel pressure gauge on it located somewhere that you can see it while driving to see if thats what its doing?

Do you have a return line on it by chance? If you do could that be plugged? Does your regulator have a vacuum port for increasing fuel pressure as needed. How are you setting your fuel pressure. With just the pump running engine off or engine running? If it has a vacuum port that might be jacking with you.

I dont mean to insult your intelligence an any way by asking these questions. Just throwing out some ideas.

Gene