LQ4 Swap Rough running

[billrobbobjo]

I have put a LQ4 6.0 out of an express van into my truck, 1957 chevy. I currently have it running and the motor is bone stock from how GM sold it. I have 2 O2 sensors w/ cherry bombs off the stock exhaust manifolds. I have deleted a few wires out of the harness, stuff that that LT1swap.com said i didnt needed. Long story short the motor will run but once I w/ a load on it, it struggles. I can rev it up to about 3500 rpm. I have check the fuel pressure which I unhook the vacuum and get 55-58 pounds when i hook it back up I have 48 PSI. When i rev it the vacuum pulls the dial around, which seems to work normal. I have swapped the Plugs and wires, I have been messing with the fuel pump and lines these are 3/8 inch. Currently I have the pump in the tank with it free floating. I checked most some injectors w/ a Noid light. All of it seems to work pretty well. When the motor starts to act up it struggles to run it seems to only run on 2 or 4 of the cylinders (slow running/ exhaust feels different when it fires. If it pulls out of the struggle it runs normal again. I havent ever really had the motor moving in this truck before. First week w/ it running. Any tips or advice?

[Captainfab]

Does the PCM have the stock tune or have you had it modified to fit your needs and deleted connections? FYI, you might get more responses if you have a mod move this to the LSx swap section.

[billrobbobjo]

It is a stock tune minus the VATS.

[Super73]

Does it have everything stock? IE manifolds, intake, intake tube, maf, filter box etc?

If not, there is a good chance the ECU is confused and not controlling fuel/timing correctly for the combo