Fitech running fat

Dubob said
I’m not an expert but if it were me I’d temporarily run a return from the tbi and see what happens. Just takes a little time to remove the regulator guts, if it’s similar to Holley, and a return line to see. It can get frustrating. Sometimes we run into issues that “tech” hasn’t seen, or don’t want to work thru. In my case it wasn’t a psi issue but I believe a volume issue that couldn’t keep up with varying demands. Have you installed a new set of plugs also.

Yes e3s and there is already a return from the tbi to the reg.

JoeSBP said
Just read through and wanted to verify the issue.
What is the relation of the displayed AFR vs Target AFR?
1. Is the system aware/displaying that it's rich, but just not capable of leaning down to the Target AFR?
2. Or is the system displaying it's at Target AFR, but is in fact rich?

1. This could be a result of excessive fuel pressure. You have it regulated down to 43psi, but I strongly suggest installing a gauge at the throttle body to ensure it is in fact seeing 43psi. Also where is the IAC?
2. This could be a result of an exhaust leak, or non-optimum O2 sensor placement. Where is the sensor installed?

The system displays its at target afr but still running rich. IACs are 3-4. O2 sensor is 3" behind collector, welded bung. No exhaust leaks anywhere. Thanks for your input!