I think this is pointing to the fuel pump. I'd suspect the high pressure fuel pump. But this doesn't explain the epc light.
The alternative thing could be to get the battery tested to see if it's working correctly. Just in case it's failing and throwing up fault codes.
So stage 2 straight through exhaust such as powerflow etc.
Better injectors, turbo and intercooler.
Then remap. Don't forget to get the gearbox mapping looked at afterwards too.