My bet is on a faulty rear fuel pump as well
I went through all the above steps (o-rings, plugs, fuel filters, over boost relay, etc.....) none of these items fixed the problem. If I didn't accelerate too quickly, I could get the car to rev up to 6K rpm (low fuel demand), but when I put my foot into it, she cough hard at 4k rpm's and only recover if I lifted.
$350 for a new pump and I've never had a return of the issue.
If you get it resolved you must chime in with what fixed the issue.....it helps everyone out.
Good luck,
Blaine