Still have low O2 millivolts

[2QWIK4U]

I've been chasing a low O2 millivolts problem. I only get to work on my GN every month or so due to work and parenting so it may take me awhile to try different solutions.
I started noticing O2 counts in the 460-550 range at WOT with Turbo Tweak street chip ,50 lb injectors and a mild 12-25 lbs of boost. Fuel pressure would not go over 50 psi at wot. I installed 140 alternator,no change. Just finished installing new Racetronix fuel pump and fixed a bad connection to pump. It is hot wired. Now fp will rise to 58-60 lbs at wot but millivolts were only 464!!!! With 1.6 kr.
Tried to adjust fp and now it won't move off 46 at idle. Checked vacuum on fp regulator and it'll only go to 15 and starts dropping.
Is this my problem and where can I get a rebuild kit for it?

 

[2QWIK4U]

That should read 12-15 lbs of boost and need to mention I installed new DENSO O2 sensor with no change

 

[bpman1234]

What fuel pressure regulator do you have ?

 

[2QWIK4U]

I can't recall where I bought it but I think it was ATR or Conleys years ago Its black with 4 Allen head bolts holding it together. I did notice a few minutes ago that it will now raise fp but go no lower than 48 psi.

What fuel pressure regulator do you have ?

 

[bpman1234]

Atr? Think there's a rebuild kit for it the diaphram must be leaking if you can't get fuel down also check for restriction on return line.

 

[2QWIK4U]

During the install of new pump today there seemed to be alot of fuel draing from return line. I don't recall that the last time I had tank out but it's been a long time. I went ahead and replaced fuel filter with new Delco also. I dont think there's any way the lines are hooked up wrong as someone asked me earlier.
What's the easiest way to check the return line?

 

[2QWIK4U]

Who sells a rebuild kit for regulator?

 

[No disintegrations]

If your fuel pressure is 60 psi when you're on it I don't think that's the problem. That's the correct pressure for 15 boost. Low o2 could be from a missfire, unburned air fuel mix goes out the exhaust and is read as lean. Do you think it might be misfiring or breaking up?

 

[2QWIK4U]

Doesn't seem to miss or break up at all. It pulls hard but I let off the gas quick since counts are so low.
Has new NGK plugs,10 mm wires and coil/module aren't very old

 

[No disintegrations]

Also I wonder why you're getting knock on basically stock boost level. Running 93 octane?