Kecrew

4.8 rebuilt to 309 stock heads with btr 660 kit ljms stage 2 cam chromoly pushrods mls gasket and head studs stock truck intake 80 lb injectors on stock truck return style system aem 380 lph in line pump gt45 eBay turbo, it leans out anything over quarter throttle most I've seen is 2psi before it leans out, did a data log today duty cycle was 9% driving before it would lean out , in park revving to 6100 it was 20% what could be the issue?

Old Geezer

iTrader: (3)

A couple things....
Post a data log and the tune.
Post a sketch as to how the fuel system is plumbed.
Check the fuel psi during this event.

Fullpower

What is static fuel pressure, ie key ON, engine not running ?
What is fuel rail pressure at engine idle speed ?
What is (measured) voltage AT fuel pump ?
Where is fuel pressure regulator mounted ?
Where is fuel pressure regulator manifold pressure reference connected ?

eaglegoat

Has it been tuned? What changes were recently made after tuning?