[MetroMPG]

The counter-argument is: the RPM at which you run an engine when driving for maximum efficiency are low enough that there isn't a significant restriction in the intake or exhaust to be fixed by changing out those bits. Plumbing mods have their biggest impacts at high flow rates (ie. high RPM).

But again: why are we talking about mods in the driving technique thread??? Starting a new topic, or posting in an existing one would be best.