So car runs on E85 90% of the time, unless I am in a pinch and can't find any, or I am flushing some 93 through once in awhile to flush the system. But I have a stock in tank pump and a AUX pump. Added a return setup, but never dropped the tanks, so its at the base pressure of 58psi.

Anyways, car has sat for months before with no issue. Latest time it sat was for a month. Take it out and I notice it seems to fall on its face after say 5k rpm. And the AFR is at high 12-13. Typically it would be mid 10s (It runs a little fat) Though maybe some water was in the tank. Burn through the tank and fill it with fresh E. Then after some time it will now pull all the way to 7100 no issue, but the AFR is still high 12-mid 13s on a pull. This is at WOT. If i got 1/2-3/4 throttle, it will be in the 11s.

I did have a loose ground and my alternator wasn't giving me a consistent 13-14v, and I replaced my battery. I've also put a external manual fuel gauge on it that I can watch while doing a pull, and at WOT the pressure drops every so slightly then the AUX fuel pump comes on (on a hobbs switch) and stays at a steady 58psi. So if i am maintaining pressure, could the injectors be the issue? Perhaps send them off to be cleaned and checked? Maybe the wideband needs to be recalibrated? I bought a set of fresh plugs, though about making a pull, shutting it off and pulling them to see if it is in fact lean.

Any ideas?

 

So, nothing changed from prior to letting it sit, to now that it's having issues? Did you have a way to monitor fuel pressure before all this? Has it always been 58psi under boost?

 

Nothing changed. I hooked up a remote manual pressure gauge and monitored it while masking a pull and it stayed at a solid 58psi the entire time. I sent my injectors off to be cleaned and checked, and they came back good. No too much variation or issue. So no smoking gun there, unless behind a little clogged caused it.

I am assuming maybe my pumps are pumping enough but not having the flow? Next step I will go out to make a pull, put fresh plugs in and then make a pull, shut down and read them.

 

If its at 58psi during wot boost and going lean with good injector quality the only explanation is the tuning. But since tunes dont magically change it must be something related to the tune such as maf sensor or map sensor. It goes maf -> ecu -> injectors. Or map. For example maf is dirty. Or maf is leaking air somehow. Or the boost has gone up without you noticing and its not tuned for that. Depends on whether turbo/sc they handle boost changes differently. For example if an exhaust restriction is removed for turbo the engine can flow more at the same boost. but if that happens to a sc car the boost just drops as a result.

Another possibility is misfires which present as lean spikes. For example plug gap is growing larger or fouling up and subtle misfires can occur and raise the afr.
Another possible is the fuel pressure gauge is wrong and its actually dropping. Or being measured from the wrong spot.

Another possibility is incorrect afr due to some inducted air to the exhaust (exhaust leaking). Or some issue with wideband sensor warming / temperature. Sensors too close to the turbo sometimes have this issue they get cooked. It should be at least 4 or 5 feet from a turbine / engine.

All that aside your fuel system could use optimization. 58psi is a poor choice for forced induction v8 fuel systems. Ideal fuel pressure is about 38 to 41psi with optimum injector size enough to fit fuel into post EVC of approx 300 degrees to 230 degrees before TDCC, so around 30 to 40% duty cycle approaching peak torque for this window. The fuel regulator should be referenced. If yours is not referenced then the fuel pressure drops with increasing boost and could be part of the issue here somehow related, depending how its tuned.