[tobiasgriffith]

I've had my Echo since 2000 and it's been a very good car until about 9 months ago.
It all started when, after the car had been sitting a few hours or more, it would struggle a little once you started your first acceleration. It would almost stall, and then miraculously, after only one time, drive normally until the next time.
About 4 months ago, the check engine light came on, stayed on for about a day or so and then went back off again.
About 2 months ago, driving long distances with it, I was going about 75 mph on the freeway and it suddenly gave way, dropping my speed to about 35 and I pulled over, waited a few minutes and started it again and drove home. The check engine light came on and has since never gone off again.
Now, not only do I have the "almost stalling" problem all the time, but after this passes, it makes a slight rattling noise as I accelerate around the 30 mph range (automatic transmission).
I finally took the car to auto zone earlier today and had them test it and tell me that the oxygen sensor needs to be replaced "too lean". I bought the sensor with a set of spark plugs and then began my quest to discover how to change the oxygen sensor. Good thing I came accross this website and have read what I've read. I immediately cleaned the MAF sensor and dried it with an air compressor, pulled the EFI fuse and reset the check engine light.
Not only did I feel the difference immediately but I've driven 30 miles now and the light did not return.
The only thing that worries me is I still hear that slight rattling noise when accelerating around the 30 mph range. Do I need to clean my throttle body and if so, what do I use to clean it? I've seen the file, but would like more specific info on this as I'm not too "car savvy".
I'll let you know if the check engine light comes back on, but as of now, so far so good.

Thank you very much for all your help.