Soup bowl your intake, different exhaust to start with.
Later on you can move up to a turbo and some other mechanical parts.
I haven't seen over 20mpg in our idi so yea not much of a fuel saver, but it will walk the dog and kick the cat once you get them modified. Just watch your internals. Keep the coolant additive in at all times to prevent cavitation too, I'm not saying it WILL cavitate, we ran ours without it alot. Just to be safe run it with the additive.
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