1997 Ford Thunderbird 97 3.8 no power

I have a 1997 3.8 Thunderbird. It starts, idles fair a little miss, put it in gear hit the gas; well my grandmother can walk faster than this car. Code is po155, po165 alright changed them, clear codes to find out the same thing, no change. Removed the exhaust, started it up, same thing. Next thing I changed plugs, wires, changed gas filter, seemed to run good at start up but went back to no power. Frustrated