P0171 P0174 Codes

I have a 2006 Range Rover HSE 4.4 it keeps giveing me these Code, I have flash and update the ECU Done a smoke test, propane test, change egr valve, change the o2 sencors, now after you drive about 15 miles the engine light come on, put some Sea Foam in the tank, some one told me to try to Blanking the engine Compartment where the hose come in the inside,, could some one please tell me what Blanking mean? and any advice would be help. Thanks