I have my EGR disabled (EGR valve vacume hose disconnected with EGR block plate in) on my 400 and don't have any pinging problems with 85 oct gas. I bought Edelbrock non-EGR intake manifold as it'll get rid of the whole EGR system for cleaner look. I'd test to see if your engine will ping with EGR disabled, and if it doesn't, go for it!