EGR Valve P0404 and P0405 code, loss of power TTID

P0404 Code p0404 The vehicle lacks of power When I clear the p0404 fault code, the vehicle runs great for a couple of days or miles (costumer mentioned that p0404 The glow plug light flashes all the time after around 3 mins after you start the van I took it to a garage and they read the fault code which was P0404 EGR

p0404 EGR Valve Code P0404 and this code came up, will changing the EGR valve solve the issue or is it a more demanding task ? Is it a difficult