do you in the US still have E5 as normal or have you gone E10 as well? has it effected your cars?
It varies by state. NJ has between 5-10, but higher octanes tend to have less. I always run 93 RON (highest you can get on road pumps here). Had a few problems when it started:
[1] I run HIF6's on my car. The downside is the float chambers are at the bottom of the carb bodies. In 88F (31C) and hotter weather the float chambers would boil causing the floats to drop and the chambers to overflow. Ethanol lowers the boiling point pretty dramatically I discovered (Took a good six weeks of tail chasing to find out the cause of the overfuelling!). My solution was to add 3mm thick self adhesive glass fibre heatshielding to the original heat shield. I added to both sides, it also has a reflective foil film. This has cured the problem since then. Including 100F (37C) days and sessions on the track.
[2] the O ring in the fuel reserve tap needs to be replaced with a viton rubber O ring (ethanol attacks regular rubber)
[3] Replace the diaphram in the fuel pump (same reason as No 2 above). Mine failed at higher temps, again due to ethanol.
[4] If you have a rubber hose between the carbs or anywhere else on the fuel system, replace with E10 proof fuel line. you DO NOT want an engine fire!
On a note about running on ethanol fuel. I found a slightly richer needle helped avoid flat spots caused by the lower grade fuel.
If leaving the car standing for a few months buy some fuel stabliser and fill the tank (counter intuitive I know). Ethanol likes to absorb moisture from the air. By having a full tank there's less air exposure, so less available moisture. Ethanol fuel tends to go off after about 6-12 months. The stabliser with help combat this. The car will run on old fuel, but it won't be happy.
I think that's about it.