less air intake
 

would less air going into the air intake help on mpg?

your engine is a positive displacement pump the slower it turns the better your fuel consumption should be, so I would say yes.

couple of things to consider:

how is your ECM measuring airflow? MAF or speed-density?

if you alter the VE via intake changes so that less air is entering the engine for a given RPM and manifold pressure, the MAF system will adapt, since it only measures airmass, but a speed-density engine would actually run richer due to the ECM thinking more air is entering the engine than reality. the O2 sensor will allow for it to adapt eventually, but until then, you'll actually lose fuel efficiency.

what if its a honda d16y8. they use a map sensor?

Seems like the same affect as using less throttle, how would this be different?

okay thanks. ill try and see what happends.

A quick Ecomodder search:
http://ecomodder.com/forum/showthrea...est-19054.html

Frank sums it up quite well in that thread:
Less air going in the engine will help, but you can do that with the throttle.

That seems completely logical to me. Wonder if it would be worth running a larger intake to lean the mix out a little?

keep in mind, i'm referring to being able to effectively change the volumetric efficiency of the engine.... changing anything upstream of the throttle usually won't qualify/have enough of an effect. sure, you could (for example) suck hotter air and have the air be less dense, but air temp is also factored into both speed-density and MAF.