check engine light will not go off, the current code is p0402 on 2001 Toyota Camry

so far have replaced,catalitic converter (think code was 420)
along with that pcv, egr, vcv, charcoal canister,and flex pipe egr intake cleaned out with sea foam (2 months ago) yesterday cleaned out again massive amounts of carbon again. check engine light still on p402. now i am told there is a flaw with camry ports inside heads are too small carbon cannot flow out as well now 3 to 5 hours labor to cleanout. 150,000 miles. want to keep car
HELP cant afford much more to fix.

Asked by for the 2001 Toyota Camry
seek diag so you don't waste time and money
1 more answer
Code for EGR flow issues. potential causes are:
EGR Vacuum Hose(s)
Exhaust Gas Recirculation (EGR) Vacuum Solenoid Valve (VSV)
Exhaust Gas Recirculation (EGR) Valve