and where is a good place to buy one from? also how hard is the install?

 

You can get adjustable replacements for anywhere from $65-$120. I'd probably check out www.thunderracing.com or www.tbyrne.com, although I'm sure jegs some choices as well.

 

how often do they go bad and how do i check it does??

 

I've personally never heard of one going bad. However, hold of a little bit before purchasing one, and do some research. From what I understand, they won't help your car at all in the long run. When you install it, and you adjust your fuel pressure (FP) to the optimum setting, your going to probably feel a good power gain in the beginning. However, over a short period of time, the computer will just learn to compensate for any adjustments you mad mechanically, and return the air-fuel ratio to stock specs. The only way to REALLY change your air fuel ratio would be to have your vehicle's PCM tuned.
Put that $100 to the side, and save up for a dyno tune.