Still working getting the 2056 L-jet to run well.

I have a surge or miss under hard acceleration 3500rpm and above.

It doesn't happen every time and I think it is more likely to happen under rapid wide open throttle, but I can get good acceleration pulls sometimes.

If it does start to surge and I stay in it I stay on the throttle I can hear a pfft or burp of air which I think is coming out of the exhaust.

Fuel pressure (with Harbor Freight gauge) is reading 39psi under hard acceleration
Timing is set to 28 dgrees BTDC@3500 rpm
New plug wires and plugs
Cleaned distributor and regreased (running Pertronix)
Tried 2 different Bosch coils with same results

Could the fuel pump volume be out of spec and still deliver pressures like I am seeing?(what are the specs for fuel pump volume test?)

Should I try a different timing setting, more or less advance?

Could the potentiometer in the AFM be hitting a dead spot?

Or could a bad plug wire give intermittent issues like this?

Starting to get old car-ed out!

I can't remember, do you have an air/fuel meter hooked up in your car? If so, do you see any fluctuation in mixture at this point? I just installed all new fuel lines and fuel pump and I have a kink in one of my rubber hoses under the tank (I believe).....I have a very obvious fuel starvation at load. My AFR meter just takes a dive when this happens and is a good indicator of whether you have a fuel delivery problem.
Of course, your issue could still be related to your L Jet AFM or ? I've got D Jet so I've no experience with your setup but an air/fuel meter is good info to have at your disposal! Jon

If you are still using the L-Jet dual relay, be sure it is secured and not bouncing around. Second, double check the wire from the dual relay to the fuel pump. I has to be in there tight- it might be vibrating a tiny bit and interrupting the circuit.

You can bypass the dual relays fuel pump circuit by grounding III on the relay board, that would be the 4 spade connector in the rear left corner.