1995 Ford Windstar rough idle

Engine Performance problem
1995 Ford Windstar 6 cyl Front Wheel Drive 148000 miles

Hello there some weeks ago there was an issue with the gas this van always had to run on midgrade non ethenal gas so my wife decided to go put the mid grade with the ethenal gas because of cheeper. Since then been running crappy.I did get a code it said o2 sensor bank 1 down strem fail at this point realy running rougth idle spitin, sputering, stalls at stop signs, lotts of water from tail pipe. I changed gas back to what it was, changed gas filter, changed air filter. Somewhat helped. Put in carb/injector cleaner in gas, still running like crap, now has no pickup at all when give the gas to go like put the pedle to the metal, you can here a bogging in the airfilter area. Acting like trans slipping. So then I changed tran filter/fluid NO go still the same. I changed both cats acting like back pressure, still the same NO POWER vrey frustrating. The bigist thing (rough idle, no pwer, boggs down on passing on interstate, going uptill, won't go past 65 mph)Now I have a fast idle problem takes a long time to come down to noraml but now when give any gas goes high fore awhile then comes down. Do you have a stick of tnt. So far I've changed gsa filter, air filter, both cats, IAC, EGR, TPS, crank sensor, cam sensor, all intake gasgets, plugs/wires. Still not receiveing any codes. I'm very puzzled I've run into this before on a Buick Skilark had sme type simtums I couldn't figure out that one eathere well thats it could someone shead some ligth pleaseI am a fellow mechanic for 30 someodd years on all types of vehicals. Please Help I can't aford puting in more money or another car. Thank you Richard