in the real world i am a petroleum distributor for a number of large
refineries. as part of the govt mandated change from mtbe to ethanol
additized gasolines our industry has been faced with a lot of
conversion problems related to the changeover. as an example all of our
underground storage tanks had to be thourougly cleaned which in some
cases meant we had to put men down in the tanks to make absolutely
certain the tank bottoms were both dry [water is typically found in the
bottoms of gasoline tanks as a result of natural condensation] and
clear of any soluble debris that oftentimes finds it way into storage
tanks. the primary problem being water as since gas will not absorb
water product will float on top of any water in the tanks. this is not
usually a problem since the submerged turbine pumps that lift the
product from the tanks bottoms are cut off at anywhere from 6 to 12
inches from the bottom of the tank.                               with
the introduction of ethanol that all changed because ethanol will
absorb water which of course in any quantity will raise havoc with any
internal combustion engine. as a result not only do the tanks have to
be cleaned of water but they must also be continually monitored so that
when water appears [as it will inevitablely] a stop sale on the product
will be instituted. additionally the  indusrty has developed a filter
which should be installed on the fuel dispensers [gas pumps] which will
shut off the flow as soon as any contaminated product is detected.
                                                 the other probably
more  significant issue is that all gasoline leaves a varnish type
residue which is found in virtually every system the product touchs.
ethanol is a solvent for varnish so the ethanol additized product is
actually stripping the accumulated varnish from the underground storage
tanks, piping, gas pumps, car fuel tanks, fuel lines, carbs, injectors,
manifolds etc.
                              with all the above as background what we
are probably experiencing is some water dilution of the ethanol along
with the varnish scrubbing effect which is resulting in rough idling
etc. my guess is that the more ethanol additized product you burn the
cleaner your fuel system will become and the quicker your performance
issues will resolve. my advice is to be patient and wait for the new
fuels to do their job  BEFORE  you start fooling around with fuel
mixtures etc. hope the above helps. ed ellis

What I tell my customers is to add a fuel filter between fuel tank and
fuel pump and a second filter between fuel pump and carburetor.  Use a
see-thru type disposable filter and have both filters the same.  As the
filter darkens from fuel system being cleaned you replace the primary
fuel filter (tank to pump) with the secondary fuel filter (pump to
carb) and put new filter in secondary position (i.e. fleet maint.
procedures) this way you are only buying a new secondary filter.  Also
keep eye on fuel pump gaskets, carb gaskets and any fuel system rubber
components (fuel line to accel pumps) for deteriation.  I only use fuel
injection quality hoses anymore.  We need to adapt and I personally
feel better using the new fuel blends vs. the older blends with
"patchfuk" chemicals.