during WOT:
When in PE the O2 (NB) reads around 900 mvolts.
When I'm at about 4500-4800 rpm the O2 start to drop...
from 900mV to850 to 700... to 600 ...to 500 to 450 200 to 30...

I think i'ts the fuel pressure (I have the stock one on my 383..) but I can't understand how is it possible that I haven't Knock counts!
It seems there is a lack of fuel so i'm expecting a hard detonation..
Someone had this problem?
Thanks
-Beppe-

 

knock is more difficult to have at higher RPMs. If the timing isn't high enough, it will be very less likely. Lean won't make knock by itself.
You're definitely leaning out. A pressure gauge will tell most of the story if there's a supply problem. Have you measured PW/duty cycle? Have you tried adding fuel in the calibration - Lots of fuel?

I forget, aren't you boosted too? The fuel pump will have an inverse flow capability with respect to fuel pressure. That basically makes the pump smaller as the fuel pressure rises with the boost reference.

 

No boost. no power adder.
Yes, the PW is substantial flat (it decrease just some fraction), and the Inj duty cycle continue to climb up to near 80% at 5700 rpm.
Yes, I tried to add some fuel in this range. No luck..
All seems related to the fuel pump...
Thanks
-beppe-