Jeep 5.3 swap MAF flat lining at 4k RPM

[cmcb15]

Hello all!

Recently completed a 5.3/4L60E swap in my 95' YJ Wrangler. So far things are finally getting there but I have another issue that came up once I was able to get to a dyno and start tuning. When running a pull on the dyno and/or while data logging, over 4k RPM the MAF simply flat lines. We assumed a bad MAF so I replaced it with a brand new OEM Delphi MAF...same problem! I am running one 3" high flow CAT which is new, 255LPH fuel pump (new), Holley fuel rails on a stock intake (LSXRT design), 2004 LS6 cam, 10:1 compression, 243 heads. All components are new/rebuild as this was a frame off build.

In order to rule out the MAF or something else, we ran a speed density tune and it ran no issues. Does anyone know what could be causing this issue? My dyno tuner wants to run it speed density but I want to figure out what it causing the issue before I simply ignore it.

I have attached the tune and data logs I took recently for reference. Really appreciate the knowledge and assistance here!

-Domenic

[5FDP]

Fueling is going very lean when under load. Either you have a fuel pressure problem or that MAF curve needs a lot of fuel added to it. I compared that MAF curve to a stock one and you are way way lower in the upper HZ ranges compared to a stock MAF curve.

[cmcb15]

Thank you for the quick response!

I'm running an all new fuel system with a corvette style filter/regulator that from what I can tell so far is getting the fuel at the right pressure. I will double check it for sure. If you can see that the MAF curve is so much lower than a stock tune that could definitely be an/the issue?

Thanks again!