Honda civic egr valve intake ports plugged?

hello.i have a 2002 Honda civic EX,1.7L VTech.manual transmission with 102,000 miles.the CEL gave me a code p0401, related with EGR valve.i got a new EGR valve installed,code was gone,but after driving 20 miles it came back.sprayed the intake port where the egr valve seat.code was gone,but after some miles came back.also did the ECU reset with fuse #6.still the same.the car idle goes up a bit sudden and then back to normal at 2nd and 3rd gear after i stop and go, at 40mph and up runs very fine.i was told the car must have a very bad carbon buildup.last time i sprayed the 2 hole/port using a whole NAPA carburetor/intake valve cleaner.however the code came back after driving several mile.i do not have any idea what to next