SURGING PROBLEM AFTER INSTALLED SURGE TANK AND FUEL PUMP

CAR RUNNING 350kw at all wheels which is about 400kw at the wheel on US dyno.

My car is currently surging really badly once it on boost more in 1st gear, less in 2nd gear and nearly none on 3rd gear. iIts does not pick up on dyno. Below is the story when it start surging.

Its happen when i custom a surge tank and install an external MagnaFuel 2000hp fuel pump, a Wabro intank pump and a set of 1450cc. Tuned to run E85. The surge tank is like the AMS surge tank locate at the bottom of the gear boot next to the AYC pump and the big pump running along the side. I left the car at home for 2 weeks, haft of E85 still in the tank. Two week later i pull my car out and give it a run its not surging anymore. Then i gave a couple run on drag way, and a few mountain runs its all good. Then one day, the surging happen again and same thing only when on boost. Took it back to the workshop and start testing bit by bit.

* Check on dyno, nothing wrong with mapping or tunning.
* Replaced another set up injectors. STILL SURGING.
* Replace another pump. STILL SURGING.
* Check intank pump, fuel sock and lines, normal.

I NOTICE ONE THING TODAY.

Its only surging when i pump hard on the accelerator pedal. And only when on boost. But if i gently pump the accelerator pedal to the limit. NO SURGING

The only thing i can guess now is too much toques passing through the diff or my surge tank setup have problem. More toques and 1st gear and less toques in 2nd and 3rd gear. Or the fuel relay.

PLEASE HELP ME WITH THIS SURGING PROBLEM GUYS. I AM REALLY APPRECIATE.


THANK YOU.
Tuan