Help! Car stuck in limp mode

First the coil light started flashing and the car would go into limp mode. If I turned the engine off and back on it would be fine for a while.

Plugged in diagnostic tester and showed the fault code for egr p0408.

Took it to highly reputable motorsport and remapping center where they plugged in their diagnostic tester and came up with same code so did a egr delete (blanking plate) and remap.

When they finished the car was driving exactly the same in limp mode but didn't have no warning lights or error codes. They told me the car must have an underlying problem.

They said it could be a possible dpf blockage so told me to disconnect my exhaust from the turbo and check if the car drove tidy. Did this and car was exactly the same and I also checked the turbo and was running fine.

Took the car back and had the Base map put back on but now the cars coil and engine management light is back on and the same error code is back and still in limp mode.
*blanking plate still on the egr*

Since having the base map put back on ive also changed the fuel filter to eliminate that.

Help ! I'M STUCK IN A CIRCLE