Still having problems....need help

I've been going back and forth with this car for the last month, thought I'd finally fixed it this weekend and the d@mn 'Check Engine' light came on again today and noticed same problem.

Here it goes....

Was getting P1131 code. Car dies occasionally when coming to a stop (like once a week, maybe), poor gas mileage, and once I hit 60 MPH, engine runs rough. Exhaust also has a strong smell. Replaced O2 sensor (which Autozone employee recommended), seemed to run better for a day then same thing. Replaced fuel filter (again, Autozone employee recommended). Same thing. Replaced the spark plugs this weekend (they really needed it!) and checked the MAF sensor (someone here on the board recommeded this) and it looked fine, was very clean. Noticed a BIG difference, car ran great. Started driving into work today and noticed car running a little rough again when I hit 60, also noticed that it took a little more gas than it should have. Driving back to work from lunch, 'Check engine' light came on again.

I'm at the end of my rope, I can't afford to take it to a mechanic, but I can't afford to keep playing the "try this...." game. Could it be the PCV valve??? It's never been replaced and I was going to do it also, until I saw what I had to do to get to it.

Please help!

yes, it could be the pcv valve.

Dang! That looks like a heck of a job....I may try it, though.

Anyone else got any other ideas???