HELP... beginning of January I accidentally filled up the tank with E85. I know, stupid. Flushed it by filling up every 1/4 tank with premium for the rest of the month. Early February had my oil changed and new battery put in. The next night I went to town and noticed a little power drag, filled up the tank again as we were leaving the next day for vacation.
Left on vacation and the power drag continued but not all the time. We put octane booster in over other fill up to try to help. Took the truck to my brothers shop and he put it on the machine and although the check engine light was on, no codes showed up. They did change the fuel filter thinking that it might be clogged. Truck ran fine after that, and all was happy. Only time we noticed the drag was going uphill, and by now we were in the mountains in TN.
Now we have been back home in FL for a while, and the drag is back and worse than ever. Put it on the computer yesterday and it threw 7 codes at us... P1131 P1151 P1309 P0303 P0307 P0171 and P0174. They did check the vacuum lines while we were still on our trip and one had a small split in it, and that was changed/fixed.
I can't afford to put out a bunch of money right now not knowing what it might be, hubby was told that the catalytic converter(s) could be clogged, I know that it was very hot yesterday while they were checking out the truck, while the air hose in the engine that should have been hot was not at all.

If it is the cat, then it was already coming. Some computers get well out of calibration and take a while to come back. Ethanol has a tendency to loosen up the deposits left by regular gasoline, so a good fuel system cleaning may be in order. Try running a can of Sea Foam brand cleaner through it.

So what does a fuel system cleaning entail? He is supposed to be getting to work on the truck this afternoon.

You can have one hired, but the one I mention is simply put a can in the tank, fill it up, and drive it through...

E85 i dont think will clog a cat. That was slready in the cards. But it can cause power loss. Did it seem to lose power going slow (like under 2000 rpm) or when you really got on it? Also keep in mind high elevations eat power.

Prolonged use of E85 will eat away seals etc

E85 in and of itself will not do anything to a cat. It will take out seals if they are the older natural rubber, but will not harm the neoprene seals.