Oxygen Sensor

On my 96 Tacoma my check engine light came on. I checked the code and it was a power train 171 which is bank 1. I changed my #1 O2 sensor before the cat and cleared the code. a couple days later the code appeared again. I went ahead and changed the #2 O2 just to take that variable out of the equation and cleared the code. about a week later it came back on again. I dont know what else to do. i checked all the hoses thinking i might have a vacuum leak but there were no leaks. I have a pinhole leak in my headers that i have had on there for about 6 years but im not sure if that small leak would create the code. the hole is located where all four pipes become one. Any help would be greatly appreciated. The code is affecting my gas mileage and how my truck starts at certain times. Thanx

 

uhhh specific code # please. Looks like it's a '96. Mileage? have you cleaned your MAF?

 

Bad cat?

 

The code is a #171. I have already cleaned the MAF also. The Cat is still good.