If its a daily driver and you live in colder winter areas, repair it, if your local state laws prohibit alteration of emissions, repair it, Federal law requires you keep it and repair it if you drive it on public roads and or have it tagged. On the other hand live in only warm areas, delete it. only race it, trailer it around, delete it, want less parts, more room, delete it, if you your states does not emission tests diesel cars, delete it if you must.
i would keep it and repair it properly this time around. Only because its going to cost you more to delete it with a tune to fix the EGR CEL