will not hold rpm only while moving

[Hooker1]

I am having an issue that I have never come across that has me stumped. LS Swap into a square body. Truck starts and idles perfect. Does great shifting into drive and reverse (no stumbling). Can foot brake the truck over 3k in drive or reverse without it cutting out. Here is the problem, as soon as the truck is moving forward or reverse it will accelerate normally for a few seconds and then fall on it's face (but will not die). It will pick up after a few seconds and start to run again for several more seconds then do it again. If your moving fast enough between it cutting out and picking back up it will shift into the next gear without an issue but will again cut out and recover (over and over). I have attempted to drive it in only first gear and it does the same thing.

I have changed the PRNDL settings to all 3 options hoping that would do something but it does not change anything.
I have also checked the TAC module and pedal and all is good there.

Something is sending a signal that is causing to cut out while moving but I am lost at this point. I'm sure it's something someone else has run across and is probably minor. Any help at all would be great, I should have had this running months ago.

Motor and trans info: 2001 suburban with 4L60 with factor 411 ECM. Motor is stock except for shorty headers and the emissions removed. Has new MAF and MAP. It is a drive by wire.

[Lakegoat]

Where is the maf located? Where did you get the maf and map sensors?
Turn off the maf and see if it will run in sd---if your map sensor is genuine GM

[kevin87turbot]

It's very likely a fuel delivery problem. Each rpm dip also has a corresponding dip of O2 sensor voltage. Very likely a fuel pressure dip.

[WAcord]

eng-airflow-dyn-high rpm disable ;it is set to 40rpm ? not 4000

[Hooker1]

Still does ot in sd. MAF is about 12 inches from TB right next to the filter. It's a dry filter setup. Sensors are Delphi

[Hooker1]

I noticed the STFT is climbing up high right before it shuts down.

[Hooker1]

eng-airflow-dyn-high rpm disable ;it is set to 40rpm ? not 4000

Thank you. I'll change it and see what it does.

[Hooker1]

I disconnected the VSS and it would only stay in first gear but it did not cut out at any rpm. Connected the VSS back up and it went back to cutting out. I put a new VSS in and it does the same thing. I have good connections between the VSS sensor and the PCM (both wires).

[Hooker1]

It's very likely a fuel delivery problem. Each rpm dip also has a corresponding dip of O2 sensor voltage. Very likely a fuel pressure dip.

I'll put a gage on it and see if it drops before the cut out. Last I checked it I had 110psi prior to the regulator on the rail.

[WAcord]

eng-tq management-etc limits-etc tps max you have at 100 /try stock settings and disable abuse mode in tran-tq man. I am new to tuning ,but see if that helps

[Hooker1]

Thank you. I'll change it and see what it does.

Changed it back to 4000. Didnt make a difference

[Hooker1]

It's very likely a fuel delivery problem. Each rpm dip also has a corresponding dip of O2 sensor voltage. Very likely a fuel pressure dip.

Checked it with a guage. No pressure drop at the rail. Stays at 50 psi and only drops to 47 after it cuts out.