>>>*This report is interesting and I have heard it before. At this point I still cannot completely explain the few reports of chattery idle, except that typically I hear it combined with exhaust system improvements.

I was listening to one a few weeks ago that fired up in one of our local dealer's shops, stock manifold with 2" into 2 1/4" and EFI. It sat there running at 850 and I would guess I could set an egg on the valve cover and have it stay there.

Of course my son Tod built it, fully balanced and quenched with just the StreetRV head and the 261C camshaft, nothing fancy. Just a sweet street setup.

Still, every once in awhile I have someone even send one back, completely unable to figure it out. So far, 100% of the time I have checked, cleaned it up and sold it as used and next time it runs just like we expect...???

On mileage, all the dyno tests we did were at sustained throttle with the fuel curve read at a specific RPM. There was zero difference, the same as math indicates and that convinced me. Those tests are always run at full throttle/full load or part throttle/full load so they don't duplicate real world that well, they are done for comparisons.

Typical daily driving is almost constant throttle motion.

The folks who DO report mileage gains without fail I suspect have a heavier foot than others. This makes some sense as added power gets a vehicle up to speed more quickly and more fuel is used getting up to speed than cruising by far. I can't explain the reports of improvements on trips, the fact is there should be no difference.

But as always, I find myself interested....*EB