sensor questions
 

So I'm going to replace the o2 sensor in my '90 Golf and I've noticed that the prices are all over the place. What are the real differences between the different brands, and what should I look for and/or avoid? If all I'm paying for is the name brand then I don't care, but I'd rather throw down a little bit and get a quality sensor if it'll make much difference in the performance of my car.

Anyone have any thoughts on this?

Also, how does one test your o2 sensor or your MAF to know if its still working properly?

Check eBay I bought some unversal 4 wire sensors there a few years ago and they are just as good as the ones you buy at the auto parts for $60-$70. The only thing with the unversal is you have to cut the plug off of your old one and spice the wires together using heat srinks. I think I paid $20. each when I bought mine. I don't know if they are still available or not since I haven't needed any so I have not checked. When I got mine there were several people selling them.